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Document And Entity Information	12 Months Ended
Document And Entity Information	Dec. 31, 2017 shares
Document Information [Line Items]
Entity Registrant Name	Tenaris SA
Entity Central Index Key	0001190723
Trading Symbol	ts
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)	1,180,536,830
Document Type	20-F
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Income Statement - USD ($)
shares in Thousands, $ in Thousands

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Continuing operations

Net sales

$ 5,288,504

$ 4,293,592

$ 6,903,123

Cost of sales

(3,685,057)

(3,165,684)

(4,747,760)

Gross profit

1,603,447

1,127,908

2,155,363

Selling, general and administrative expenses

(1,270,016)

(1,196,929)

(1,593,597)

Other operating income

10,516

21,127

14,603

Other operating expenses

(9,359)

(11,163)

(410,574)

Operating income

334,588

(59,057)

165,795

Finance Income

47,605

66,204

34,574

Finance Cost

(27,072)

(22,329)

(23,058)

Other financial results

(43,550)

(21,921)

3,076

Income (loss) before equity in earnings of non-consolidated companies and income tax

311,571

(37,103)

180,387

Equity in earnings of non-consolidated companies

116,140

71,533

(39,558)

Income before income tax

427,711

34,430

140,829

Income tax

17,136

(17,102)

(234,384)

Income (loss) for continuing operations

444,847

17,328

(93,555)

Discontinued operations:

Result for discontinued operations

91,542

41,411

19,130

Income (loss) for the year

536,389

58,739

(74,425)

Attributable to:

Owners of the parent

544,737

55,298

(80,162)

Non-controlling interests

(8,348)

3,441

5,737

Income (loss) for the year

$ 536,389

$ 58,739

$ (74,425)

Earnings per share attributable to the owners of the parent during the year:

Weighted average number of ordinary shares (thousands) (in shares)

1,180,537

Basic and diluted earnings (losses) per share (in dollars per share)

$ 0.38

$ 0.01

$ (0.08)

Basic and diluted earnings (losses) per ADS (U.S. dollars per ADS) (*) (in dollars per share)

^[1]

0.77

0.02

(0.17)

Continuing and discontinued operations

Basic and diluted earnings (losses) per share (in dollars per share)

0.46

0.05

(0.07)

Basic and diluted earnings (losses) per ADS (U.S. dollars per ADS) (*) (in dollars per share)

^[1]

$ 0.92

$ 0.09

$ (0.14)

[1]	Each ADS equals two shares.

Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Line Items [Line Items]
Income (loss) for the year	$ 536,389	$ 58,739	$ (74,425)
Items that may be subsequently reclassified to profit or loss:
Currency translation adjustment	151,762	37,187	(256,260)
Change in value of cash flow hedges	4,502	(7,525)	10,699
Change in value of available for sale financial instruments			2,486
Income tax relating to components of other comprehensive income	23	(23)	(284)
Share of other comprehensive income of non-consolidated companies:
- Currency translation adjustment	(9,548)	3,473	(92,914)
- Changes in the fair value of derivatives held as cash flow hedges and others	512	421	(3,790)
	147,251	33,533	(340,063)
Items that will not be reclassified to profit or loss:
Remeasurements of post employment benefit obligations	(8,635)	(230)	14,181
Income tax on items that will not be reclassified	1,338	(1,760)	(4,242)
Remeasurements of post employment benefit obligations of non-consolidated companies	(376)	(5,475)	(449)
	(7,673)	(7,465)	9,490
Other comprehensive income (loss) for the year, net of tax	139,578	26,068	(330,573)
Total comprehensive income (loss) for the year	675,967	84,807	(404,998)
Total comprehensive income (loss) for the year attributable to:
Owners of the parent	683,531	81,702	(410,187)
Non-controlling interests	(7,564)	3,105	5,189
Total comprehensive income (loss) for the year	675,967	84,807	(404,998)
Total comprehensive income (loss) for the year attributable to Owners of the parent arises from
Continuing operations	591,989	40,291	(429,317)
Discontinued operations	91,542	41,411	19,130
	$ 683,531	$ 81,702	$ (410,187)

Consolidated Statement of Financial Position - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement Line Items [Line Items]
Property, plant and equipment, net	$ 6,229,143	$ 6,001,939
Intangible assets, net	1,660,859	1,862,827
Investments in non-consolidated companies	640,294	557,031
Available for sale assets	21,572	21,572
Other investments	128,335	249,719
Deferred tax assets	153,532	144,613
Receivables, net	183,329	197,003
Non-current assets	9,017,064	9,034,704
Inventories, net	2,368,304	1,563,889
Receivables and prepayments, net	143,929	124,715
Current tax assets	132,334	140,986
Trade receivables, net	1,214,060	954,685
Other investments	1,192,306	1,633,142
Cash and cash equivalents	330,221	399,737
Current assets	5,381,154	4,817,154
Assets of disposal group classified as held for sale		151,417
Total assets	14,398,218	14,003,275
Capital and reserves attributable to owners of the parent	11,482,185	11,287,417
Non-controlling interests	98,785	125,655
Total equity	11,580,970	11,413,072
Borrowings	34,645	31,542
Deferred tax liabilities	457,970	550,657
Other liabilities	217,296	213,617
Provisions	36,438	63,257
Non-current liabilities	746,349	859,073
Borrowings	931,214	808,694
Current tax liabilities	102,405	101,197
Other liabilities	197,504	183,887
Provisions	32,330	22,756
Customer advances	56,707	39,668
Trade payables	750,739	556,834
Current liabilities	2,070,899	1,713,036
Liabilities of disposal group classified as held for sale		18,094
Total liabilities	2,817,248	2,590,203
Total equity and liabilities	$ 14,398,218	$ 14,003,275

Consolidated Statement of Changes In Equity - USD ($)
$ in Thousands

Issued capital [member]

Legal reserves [member]

Share premium [member]

Currency translation adjustment [member]

Other reserves [member]

Retained earnings [member]

Equity attributable to owners of parent [member]

Non-controlling interests [member]

Total

Balance at Dec. 31, 2014

$ 1,180,537

^[1]

$ 118,054

$ 609,733

$ (658,284)

$ (317,799)

^[2]

$ 11,721,873

$ 12,654,114

$ 152,200

$ 12,806,314

Statement Line Items [Line Items]

Income (loss) for the year

(80,162)

5,737

(74,425)

Currency translation adjustment

(255,569)

(691)

(256,260)

Remeasurements of post employment benefit obligations, net of taxes

10,213

^[2]

10,213

(274)

9,939

Change in value of available for sale financial instruments and cash flow hedges net of tax

12,484

^[2]

12,484

417

12,901

Share of other comprehensive income of non-consolidated companies

(92,914)

(4,239)

^[2]

(97,153)

Other comprehensive income for the year

(348,483)

18,458

^[2]

(330,025)

(548)

(330,573)

Total comprehensive income (loss) for the year

(348,483)

18,458

^[2]

(80,162)

(410,187)

5,189

(404,998)

Acquisition and other changes in non-controlling interests

659

^[2]

659

(1,727)

(1,068)

Dividends paid in cash

^[2]

(531,242)

(2,950)

(534,192)

Balance at Dec. 31, 2015

1,180,537

^[1]

118,054

609,733

(1,006,767)

(298,682)

^[2]

11,110,469

11,713,344

152,712

11,866,056

Statement Line Items [Line Items]

Income (loss) for the year

55,298

3,441

58,739

Currency translation adjustment

37,339

(152)

37,187

Remeasurements of post employment benefit obligations, net of taxes

(1,781)

^[2]

(1,781)

(209)

(1,990)

Change in value of available for sale financial instruments and cash flow hedges net of tax

(7,573)

^[2]

(7,573)

(7,548)

Share of other comprehensive income of non-consolidated companies

3,473

(5,054)

^[2]

(1,581)

Other comprehensive income for the year

40,812

(14,408)

^[2]

26,404

(336)

26,068

Total comprehensive income (loss) for the year

40,812

(14,408)

^[2]

55,298

81,702

3,105

84,807

Acquisition and other changes in non-controlling interests

^[2]

(1,073)

(1,071)

Dividends paid in cash

^[2]

(507,631)

(29,089)

(536,720)

Balance at Dec. 31, 2016

1,180,537

^[1]

118,054

609,733

(965,955)

(313,088)

^[2]

10,658,136

^[3]

11,287,417

125,655

11,413,072

Statement Line Items [Line Items]

Income (loss) for the year

544,737

^[3]

544,737

(8,348)

536,389

Currency translation adjustment

151,080

682

151,762

Remeasurements of post employment benefit obligations, net of taxes

(7,423)

^[2]

(7,423)

126

(7,297)

Change in value of available for sale financial instruments and cash flow hedges net of tax

4,549

^[2]

4,549

(24)

4,525

Share of other comprehensive income of non-consolidated companies

(9,548)

136

^[2]

(9,412)

Other comprehensive income for the year

141,532

(2,738)

^[2]

138,794

784

139,578

Total comprehensive income (loss) for the year

141,532

(2,738)

^[2]

544,737

^[3]

683,531

(7,564)

675,967

Acquisition and other changes in non-controlling interests

(4,743)

4,694

(49)

Dividends paid in cash

^[2]

(484,020)

^[3]

(484,020)

(24,000)

(508,020)

Balance at Dec. 31, 2017

$ 1,180,537

^[4]

$ 118,054

$ 609,733

$ (824,423)

$ (320,569)

^[2]

$ 10,718,853

^[3]

$ 11,482,185

$ 98,785

$ 11,580,970

[1]	The Company has an authorized share capital of a single class of 2.5 billion shares having a nominal value of $1.00 per share. As of December 31, 2016 and 2015 there were 1,180,536,830 shares issued. All issued shares are fully paid.
[2]	Other reserves include mainly the result of transactions with non-controlling interest that do not result in a loss of control, the remeasurement of post-employment benefit obligations and the changes in value of cash flow hedges and in available for sale financial instruments.
[3]	The Distributable Reserve and Retained Earnings calculated according to Luxembourg Law are disclosed in Note 25.
[4]	The Company has an authorized share capital of a single class of 2.5 billion shares having a nominal value of $1.00 per share. As of December 31, 2017 there were 1,180,536,830 shares issued. All issued shares are fully paid.

Consolidated Statement of Changes In Equity (Parentheticals) - $ / shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Line Items [Line Items]
Authorized share capital (in shares)	2,500,000,000	2,500,000,000	2,500,000,000
Nominal value (in dollars per share)	$ 1	$ 1	$ 1
Shares issued (in shares)	1,180,536,830	1,180,536,830	1,180,536,830

Consolidated Statement of Cash Flows - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Cash flows from operating activities

Income (loss) for the year

$ 536,389

$ 58,739

$ (74,425)

Adjustments for:

Depreciation and amortization

608,640

662,412

658,778

Impairment charge

400,314

Income tax accruals less payments

(193,989)

(128,079)

(91,080)

Equity in (earnings) losses of non-consolidated companies

(116,140)

(71,533)

39,558

Interest accruals less payments, net

11,550

(2,567)

26,622

Changes in provisions

(17,245)

15,597

(20,678)

Income from the sale of Conduit business

(89,694)

Changes in working capital

(855,282)

348,199

1,373,985

Currency translation adjustment and others

93,746

(19,203)

(98,070)

Net cash (used in) provided by operating activities

(22,025)

863,565

2,215,004

Cash flows from investing activities

Capital expenditures

(558,236)

(786,873)

(1,131,519)

Changes in advance to suppliers of property, plant and equipment

7,077

50,989

49,461

Proceeds from disposal of Conduit business

327,631

Investment in non-consolidated companies

(17,108)

(4,400)

Acquisition of subsidiaries

(10,418)

Investment in companies under cost method

(3,681)

Loan to non-consolidated companies

(7,056)

(42,394)

(22,322)

Proceeds from disposal of property, plant and equipment and intangible assets

5,443

23,609

10,090

Dividends received from non-consolidated companies

22,971

^[1]

20,674

^[1]

20,674

Changes in investments in securities

565,387

652,755

(695,566)

Net cash provided by (used in) investing activities

349,118

(98,348)

(1,773,582)

Cash flows from financing activities

Dividends paid

(484,020)

(507,631)

(531,242)

Dividends paid to non-controlling interest in subsidiaries

(24,000)

(29,089)

(2,950)

Acquisitions of non-controlling interests

(49)

(1,071)

(1,068)

Proceeds from borrowings

1,196,781

1,180,727

2,064,218

Repayments of borrowings

(1,090,129)

(1,295,560)

(2,063,992)

Net cash used in financing activities

(401,417)

(652,624)

(535,034)

(Decrease) increase in cash and cash equivalents

(74,324)

112,593

(93,612)

Movement in cash and cash equivalents

At the beginning of the year

398,580

286,198

416,445

Effect of exchange rate changes

5,834

(211)

(36,635)

(Decrease) increase in cash and cash equivalents

(74,324)

112,593

(93,612)

At December 31,

330,090

398,580

286,198

Cash and bank deposits

330,221

399,900

286,547

Bank overdrafts

$ (131)

$ (1,320)

$ (349)

[1]	Related to Ternium

General Information	12 Months Ended
General Information	Dec. 31, 2017
Statement Line Items [Line Items]
Disclosure of general information about financial statements [text block]	I. GENERAL INFORMATION Tenaris S.A. (the “Company”) was established as a public limited liability company ( societé anonyme ) under the laws of the Grand-Duchy of Luxembourg on December 17, 2001. The Company holds, either directly or indirectly, controlling interests in various subsidiaries in the steel pipe manufacturing and distribution businesses. References in these Consolidated Financial Statements to “Tenaris” refer to the Company and its consolidated subsidiaries. A list of the principal Company’s subsidiaries is included in Note 30 to these Consolidated Financial Statements. The Company’s shares trade on the Buenos Aires Stock Exchange, the Italian Stock Exchange and the Mexican Stock Exchange; the Company’s American Depositary Securities (“ADS”) trade on the New York Stock Exchange. These Consolidated Financial Statements were approved for issuance by the Company’s Board of Directors on February 21, 2018.

Accounting Policies

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of significant accounting policies [text block]

II. Accounting policies

The principal accounting policies applied in the preparation of these Consolidated Financial Statements are set out below. These policies have been consistently applied to all the years presented, unless otherwise stated.

Basis of presentation

The Consolidated Financial Statements of Tenaris have been prepared in accordance with International Financial Reporting Standards (“IFRS”), as issued by the International Accounting Standards Board (“IASB”) and in accordance with IFRS as adopted by the European Union, under the historical cost convention, as modified by the revaluation of available for sale financial assets, financial assets and liabilities (including derivative instruments) at fair value through profit or loss and plan assets measured at fair value. The Consolidated Financial Statements are, unless otherwise noted, presented in thousands of U.S. dollars (“$”).

Whenever necessary, certain comparative amounts have been reclassified to conform to changes in presentation in the current year.

Following the sale of the steel electric conduit business in North America, known as Republic Conduit, the results of the mentioned business are presented as discontinued operations in accordance with IFRS

"Non-current Assets Held for Sale and Discontinued Operations". Consequently, all amounts related to discontinued operations within each line item of the Consolidated Income Statement are reclassified into discontinued operations. The Consolidated Statement of Cash Flows includes the cash flows for continuing and discontinued operations, cash flows from discontinued operations and earnings per share are disclosed separately in Note

28,

as well as additional information detailing net assets of disposal group classified as held for sale and discontinued operations.

The preparation of Consolidated Financial Statements in conformity with IFRS requires management to make certain accounting estimates and assumptions that might affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the reporting dates, and the reported amounts of revenues and expenses during the reporting years. Actual results

may

differ from these estimates.

(

)

New and amended standards

not

yet adopted and relevant for Tenaris

IFRS

“Financial instruments”

July 2014,

the IASB issued IFRS

"Financial instruments", which replaces the guidance in IAS

39.

IFRS

includes new requirements on the classification and measurement of financial assets and liabilities, as well as a new impairment model based on expected credit losses rather than the incurred loss impairment model of IAS

39.

It also introduces new rules for hedge accounting. IFRS

must be applied on annual periods beginning on or after

January 1, 2018.

The Company will apply the new rules retrospectively from

January 2018.

Comparative amounts for previous years will

not

be restated.

The Company has reviewed its financial assets and liabilities and is expecting that the other investments categorized as held to maturity and carried at amortized cost will qualify for classification at fair value through other comprehensive income. Accordingly, Tenaris expects an increase in the valuation of its financial assets of approximately

million.

The new impairment model requires recognition of impairment provisions based on expected credit losses rather than on incurred credit losses. Based on the assessments undertaken, Tenaris expects a decrease of $

million in the allowance for doubtful accounts.

The Company does

not

expect any significant impact related to the new hedge accounting rules.

IFRS

15,

“Revenue from contracts with customers”

May 2014,

the IASB issued IFRS

15,

"Revenue from contracts with customers", which sets out the requirements in accounting for revenue arising from contracts with customers and which is based on the principle that revenue is recognized when control of a good or service is transferred to the customer. IFRS

must be applied on annual periods beginning on or after

January 1, 2018.

The Company has assessed the effects of applying the new standard and the main areas affected will be the accounting for sales of shipping services, free of charge services and rights of return.

The impact of the adoption as of

January 1, 2018

on the aggregate of revenues, cost of sales and selling expenses is expected to be a decrease of $

0.7

million net.

The Company intends to adopt this standard using the modified retrospective approach, meaning that the cumulative impact of the adoption will be recognized in retained earnings as of

January 1, 2018

and that comparatives will

not

be restated.

IFRS

16,

“Leases”

January 2016,

the IASB issued IFRS

16,

"Leases". The new standard will result in almost all leases recognized on the balance sheet, as the distinction between operating and finance leases is removed. IFRS

must be applied on annual periods beginning on or after

January 1, 2019.

The Company's management is currently assessing the potential impact that the application of this standard

may

have on the Company's financial condition or results of operations.

These standards were endorsed by the EU.

Other accounting pronouncements that became effective during

2017

have

material effect on the Company’s financial condition or results of operations.

Group accounting

(

)

Subsidiaries and transactions with non-controlling interests

Subsidiaries are all entities over which Tenaris has control. Tenaris controls an entity when it is exposed to, or has rights to, variable returns from its involvement with the entity and has the ability to affect those returns through its power over the entity. Subsidiaries are fully consolidated from the date on which control is exercised by the Company and are

longer consolidated from the date control ceases.

The acquisition method of accounting is used to account for the acquisition of subsidiaries by Tenaris. The cost of an acquisition is measured as the fair value of the assets transferred, equity instruments issued and liabilities incurred or assumed at the date of exchange. Acquisition-related costs are expensed as incurred. Identifiable assets acquired, liabilities and contingent liabilities assumed in a business combination are measured initially at their fair values at the acquisition date. Any non-controlling interest in the acquiree is measured either at fair value or at the non-controlling interest’s proportionate share of the acquiree’s net assets. The excess of the aggregate of the consideration transferred and the amount of any non-controlling interest in the acquiree over the fair value of the identifiable net assets acquired is recorded as goodwill. If this is less than the fair value of the net assets of the subsidiary acquired, the difference is recognized directly in the Consolidated Income Statement.

Contingent consideration is classified either as equity or as a financial liability. Amounts classified as a financial liability are subsequently remeasured to fair value with changes in fair value recognized in profit or loss.

If the business combination is achieved in stages, the acquisition date carrying value of the acquirer’s previously held equity interest in the acquiree is remeasured to fair value at the acquisition date. Any gains or losses arising from such remeasurement are recognized in profit or loss.

Transactions with non-controlling interests that do

not

result in a loss of control are accounted as transactions with equity owners of the Company. For purchases from non-controlling interests, the difference between any consideration paid and the relevant share acquired of the carrying value of net assets of the subsidiary is recorded in equity. Gains or losses on disposals to non-controlling interests are also recorded in equity.

Material intercompany transactions, balances and unrealized gains (losses) on transactions between Tenaris subsidiaries have been eliminated in consolidation. However, since the functional currency of some subsidiaries is its respective local currency, some financial gains (losses) arising from intercompany transactions are generated. These are included in the Consolidated Income Statement under

Other financial results

(

)

Non-consolidated companies

Non-consolidated companies are all entities in which Tenaris has significant influence but

not

control, generally accompanying a shareholding of between

20%

and

50%

of the voting rights. Investments in non-consolidated companies (associated and joint ventures) are accounted for by the equity method of accounting and are initially recognized at cost. The Company’s investment in non-consolidated companies includes goodwill identified in acquisition, net of any accumulated impairment loss.

Under the equity method of accounting, the investments are initially recognized at cost and adjusted thereafter to recognize Tenaris’s share of the post-acquisition profits or losses of the investee in profit or loss, and Tenaris’s share of movements in other comprehensive income of the investee in other comprehensive income. Dividends received or receivable from associates and joint ventures are recognized as a reduction in the carrying amount of the investment.

Unrealized results on transactions between Tenaris and its non-consolidated companies are eliminated to the extent of Tenaris’s interest in the non-consolidated companies. Unrealized losses are also eliminated unless the transaction provides evidence of an impairment indicator of the asset transferred. Financial statements of non-consolidated companies have been adjusted where necessary to ensure consistency with IFRS.

The Company’s pro-rata share of earnings in non-consolidated companies is recorded in the Consolidated Income Statement under

Equity in earnings (losses) of non-consolidated companies

. The Company’s pro-rata share of changes in other reserves is recognized in the Consolidated Statement of Changes in Equity under

Other Reserves.

December 31, 2017,

Tenaris holds

11.46%

of Ternium S.A (“Ternium”)’s common stock. The following factors and circumstances evidence that Tenaris has significant influence (as defined by IAS

28,

“Investments in associates companies and Joint Ventures”) over Ternium, and as a result the Company’s investment in Ternium has been accounted for under the equity method:

Both the Company and Ternium are under the indirect common control of San Faustin S.A.;

Four out of

eight

members of Ternium’s Board of Directors (including Ternium’s chairman) are also members of the Company’s Board of Directors;

Under the shareholders’ agreement by and between the Company and Techint Holdings S.à r.l, a wholly owned subsidiary of San Faustin S.A. and Ternium’s main shareholder, dated

January 9, 2006,

Techint Holdings S.à r.l, is required to take actions within its power to cause (a)

one

of the members of Ternium’s Board of Directors to be nominated by the Company and (b) any director nominated by the Company to be only removed from Ternium’s Board of Directors pursuant to previous written instructions of the Company.

December 31, 2017,

Tenaris holds through its Brazilian subsidiary Confab Industrial S.A. (“Confab”),

5.2%

of the shares with voting rights and

3.08

of Usinas Siderúrgicas de Minas Gerais S.A. (“Usiminas”) total share capital.

The acquisition of Usiminas shares was part of a larger transaction performed

January 16, 2012,

pursuant to which Ternium, certain of its subsidiaries and Confab joined Usiminas’ existing control group through the acquisition of ordinary shares representing

27.7%

of Usiminas’ total voting capital and

13.8%

of Usiminas’ total share capital.

The rights of Ternium and its subsidiaries and Confab within the Ternium - Tenaris Group are governed under a separate shareholders agreement.

Those circumstances evidence that Tenaris has significant influence over Usiminas, consequently, accounted it for under the equity method (as defined by IAS

April

and

May 2016

Tenaris’s subsidiary Confab subscribed, in the aggregate, to

1.3

million preferred shares (

BRL1.28

per share) for a total amount of

BRL1.6

million (approximately

$0.5

million) and

11.5

million ordinary shares (

BRL5.00

per share) for a total amount of

BRL57.5

million (approximately

$16.6

million). The preferred and ordinary shares were issued on

June 3, 2016

and

July 19, 2016,

respectively. Consequently as of

December 31, 2017

Tenaris owns

36.5

million ordinary shares and

1.3

million preferred shares of Usiminas.

Tenaris carries its investment in Ternium and Usiminas under the equity method, with

additional goodwill or intangible assets recognized. Tenaris reviews investments in non-consolidated companies for impairment whenever events or changes in circumstances indicate that the asset’s carrying amount

may

not

be recoverable, such as a significant or prolonged decline in fair value below the carrying value. At

December 31, 2017,

2016

and

2015,

impairment provisions were recorded on Tenaris’s investment in Ternium while in

2015,

an impairment charge was recorded on Tenaris’s investment in Usiminas. See Note

and Note

12.

Segment information

The Company is organized in

one

major business segment, Tubes, which is also the reportable operating segment.

The Tubes segment includes the production and sale of both seamless and welded steel tubular products and related services mainly for the oil and gas industry, particularly oil country tubular goods (OCTG) used in drilling operations, and for other industrial applications with production processes that consist in the transformation of steel into tubular products. Business activities included in this segment are mainly dependent on the oil and gas industry worldwide, as this industry is a major consumer of steel pipe products, particularly OCTG used in drilling activities. Demand for steel pipe products from the oil and gas industry has historically been volatile and depends primarily upon the number of oil and natural gas wells being drilled, completed and reworked, and the depth and drilling conditions of these wells. Sales are generally made to end users, with exports being done through a centrally managed global distribution network and domestic sales are made through local subsidiaries. Corporate general and administrative expenses have been allocated to the Tubes segment.

Others includes all other business activities and operating segments that are

not

required to be separately reported, including the production and selling of sucker rods, industrial equipment, coiled tubing, utility conduits for buildings, energy and raw materials that exceed internal requirements.

Tenaris’s Chief Operating Decision Maker (CEO) holds monthly meetings with senior management, in which operating and financial performance information is reviewed, including financial information that differs from IFRS principally as follows:

The use of direct cost methodology to calculate the inventories, while under IFRS it is at full cost, including absorption of production overheads and depreciations;

The use of costs based on previously internally defined cost estimates, while, under IFRS, costs are calculated at historical cost;

Other timing differences, if any.

Tenaris presents its geographical information in

five

areas: North America, South America, Europe, Middle East and Africa and Asia Pacific. For purposes of reporting geographical information, net sales are allocated to geographical areas based on the customer’s location; allocation of assets, capital expenditures and associated depreciations and amortizations are based on the geographical location of the assets.

Foreign currency translation

(

)

Functional and presentation currency

IAS

(revised) “The effects of changes in foreign exchange rates” defines the functional currency as the currency of the primary economic environment in which an entity operates.

The functional and presentation currency of the Company is the U.S. dollar. The U.S. dollar is the currency that best reflects the economic substance of the underlying events and circumstances relevant to Tenaris’s global operations.

Except for the Brazilian and Italian subsidiaries whose functional currencies are their local currencies, Tenaris determined that the functional currency of its other subsidiaries is the U.S. dollar, based on the following principal considerations:

Sales are mainly negotiated, denominated and settled in U.S. dollars. If priced in a currency other than the U.S. dollar, the sales price

may

consider exposure to fluctuation in the exchange rate versus the U.S. dollar;

Prices of their critical raw materials and inputs are priced and settled in U.S. dollars;

Transaction and operational environment and the cash flow of these operations have the U.S. dollar as reference currency;

Significant level of integration of the local operations within Tenaris’s international global distribution network;

Net financial assets and liabilities are mainly received and maintained in U.S. dollars;

The exchange rate of certain legal currencies has long-been affected by recurring and severe economic crises.

(

)

Transactions in currencies other than the functional currency

Transactions in currencies other than the functional currency are translated into the functional currency using the exchange rates prevailing at the date of the transactions or valuation where items are re-measured.

At the end of each reporting period: (i) monetary items denominated in currencies other than the functional currency are translated using the closing rates; (ii) non-monetary items that are measured in terms of historical cost in a currency other than the functional currency are translated using the exchange rates prevailing at the date of the transactions; and (iii) non-monetary items that are measured at fair value in a currency other than the functional currency are translated using the exchange rates prevailing at the date when the fair value was determined.

Foreign exchange gains and losses resulting from the settlement of such transactions and from the translation at year-end exchange rates of monetary assets and liabilities denominated in currencies other than the functional currency are recorded as gains and losses from foreign exchange and included in

“Other financial results”

in the Consolidated Income Statement, except when deferred in equity as qualifying cash flow hedges and qualifying net investment hedges.

(

)

Translation of financial information in currencies other than the functional currency

Results of operations for subsidiaries whose functional currencies are

not

the U.S. dollar are translated into U.S. dollars at the average exchange rates for each quarter of the year. Financial statement positions are translated at the year-end exchange rates. Translation differences are recognized in a separate component of equity as currency translation adjustments. In the case of a sale or other disposal of any of such subsidiaries, any accumulated translation difference would be recognized in income as a gain or loss from the sale.

Goodwill and fair value adjustments arising from the acquisition of a foreign operation are treated as assets and liabilities of the foreign operation and translated at the closing rate.

Property, plant and equipment

Property, plant and equipment are recognized at historical acquisition or construction cost less accumulated depreciation and impairment losses. Historical cost includes expenditure that is directly attributable to the acquisition of the items. Property, plant and equipment acquired through acquisitions accounted for as business combinations have been valued initially at the fair market value of the assets acquired.

Major overhaul and rebuilding expenditures are capitalized as property, plant and equipment only when it is probable that future economic benefits associated with the item will flow to the group and the investment enhances the condition of assets beyond its original condition. The carrying amount of the replaced part is derecognized. Maintenance expenses on manufacturing properties are recorded as cost of products sold in the year in which they are incurred.

Cost

may

also include transfers from equity of any gains or losses on qualifying cash flow hedges of foreign currency purchases of property, plant and equipment.

Borrowing costs that are attributable to the acquisition or construction of certain capital assets are capitalized as part of the cost of the asset, in accordance with IAS

(R) “Borrowing Costs”. Assets for which borrowing costs are capitalized are those that require a substantial period of time to prepare for their intended use.

Depreciation method is reviewed at each year end. Depreciation is calculated using the straight-line method to depreciate the cost of each asset to its residual value over its estimated useful life, as follows:

	Land	No Depreciation
	Buildings and improvements	30-50 years
	Plant and production equipment	10-40 years
	Vehicles, furniture and fixtures, and other equipment	4-10 years

The assets’ residual values and useful lives of significant plant and production equipment are reviewed and adjusted, if appropriate, at each year-end date. An asset’s carrying amount is written down immediately to its recoverable amount if the asset’s carrying amount is greater than its estimated recoverable amount.

Management’s re-estimation of assets useful lives, performed in accordance with IAS

“Property, Plant and Equipment”, did

not

materially affect depreciation expenses for

2017,

2016

and

2015.

Tenaris depreciates each significant part of an item of property, plant and equipment for its different production facilities that (i) can be properly identified as an independent component with a cost that is significant in relation to the total cost of the item, and (ii) has a useful operating life that is different from another significant part of that same item of property, plant and equipment.

During

2017,

the Company decided to redefine the subcategories within property, plant and equipment items, in order to better reflect the nature and intended use of the assets. Comparative figures were reclassified following the new subcategories.

Gains and losses on disposals are determined by comparing the proceeds with the carrying amount of assets and are recognized under

Other operating income

Other operating expenses

in the Consolidated Income Statement.

Intangible assets

(

)

Goodwill

Goodwill represents the excess of the acquisition cost over the fair value of Tenaris’s share of net identifiable assets acquired as part of business combinations determined mainly by independent valuations. Goodwill is tested at least annually for impairment and carried at cost less accumulated impairment losses. Impairment losses on goodwill are

not

reversed. Goodwill is included in the Consolidated Statement of Financial Position under

Intangible assets, net.

For the purpose of impairment testing, goodwill is allocated to a subsidiary or group of subsidiaries that are expected to benefit from the business combination which generated the goodwill being tested.

(

)

Information systems projects

Costs associated with maintaining computer software programs are generally recognized as an expense as incurred. However, costs directly related to the development, acquisition and implementation of information systems are recognized as intangible assets if it is probable that they have economic benefits exceeding

one

year and comply with the recognition criteria of IAS

38.

Information systems projects recognized as assets are amortized using the straight-line method over their useful lives, generally

not

exceeding a period of

years. Amortization charges are mainly classified as

Selling, general and administrative expenses

in the Consolidated Income Statement.

Management’s re-estimation of assets useful lives, performed in accordance with IAS

“Intangible Assets”, did

not

materially affect amortization expenses for

2017,

2016

and

2015.

(

)

Licenses, patents, trademarks and proprietary technology

Licenses, patents, trademarks, and proprietary technology acquired in a business combination are initially recognized at fair value at the acquisition date. Licenses, patents, proprietary technology and those trademarks that have a finite useful life are carried at cost less accumulated amortization. Amortization is calculated using the straight-line method to allocate the cost over their estimated useful lives, and does

not

exceed a period of

years. Amortization charges are mainly classified as

Selling, general and administrative expenses

in the Consolidated Income Statement.

The balance of acquired trademarks that have indefinite useful lives according to external appraisal amounts to

86.7

million at

December 31, 2017

and

2016,

included in Hydril CGU. Main factors considered in the determination of the indefinite useful lives, include the years that they have been in service and their recognition among customers in the industry.

Management’s re-estimation of assets useful lives, performed in accordance with IAS

38,

did

not

materially affect amortization expenses for

2017,

2016

and

2015.

(

)

Research and development

Research expenditures as well as development costs that do

not

fulfill the criteria for capitalization are recorded as

Cost of sales

in the Consolidated Income Statement as incurred. Research and development expenditures included in

Cost of sales

for the years

2017,

2016

and

2015

totaled

$63.7

million,

$68.6

million and

$89.0

million, respectively.

(

)

Customer relationships

In accordance with IFRS

"Business Combinations" and IAS

38,

Tenaris has recognized the value of customer relationships separately from goodwill attributable to the acquisition of Maverick and Hydril groups.

Customer relationships acquired in a business combination are recognized at fair value at the acquisition date, have a finite useful life and are carried at cost less accumulated amortization. Amortization is calculated using the straight line method over the expected life of approximately

years for Maverick and

years for Hydril.

2015

the Company reviewed the useful life of Prudential’s customer relationships, related to Maverick acquisition, and decided to reduce the remaining amortization period from

years to

years, ending

December 2017.

As of

December 2017

the residual value of Maverick’s customer relationships amount to

$193

million and the residual useful life is

years, while Hydril’s customer relationships is fully amortized

Impairment of non-financial assets

Long-lived assets including identifiable intangible assets are reviewed for impairment at the lowest level for which there are separately identifiable cash flows (cash generating units, or CGU). Most of the Company’s principal subsidiaries that constitute a CGU have a single main production facility and, accordingly, each of such subsidiary represents the lowest level of asset aggregation that generates largely independent cash inflows.

Assets that are subject to amortization are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount

may

not

be recoverable. Intangible assets with indefinite useful lives, including goodwill, are subject to at least an annual impairment test.

In assessing whether there is any indication that a CGU

may

be impaired, external and internal sources of information are analyzed. Material facts and circumstances specifically considered in the analysis usually include the discount rate used in Tenaris’s cash flow projections and the business condition in terms of competitive and economic factors, such as the cost of raw materials, oil and gas prices, capital expenditure programs for Tenaris’s customers and the evolution of the rig count.

An impairment loss is recognized for the amount by which the asset’s carrying amount exceeds its recoverable amount. The recoverable amount is the higher between the asset’s value in use and fair value less costs of disposal. Any impairment loss is allocated to reduce the carrying amount of the assets of the CGU in the following order:

(a)

first, to reduce the carrying amount of any goodwill allocated to the CGU; and

(b)

then, to the other assets of the unit (group of units) pro-rata on the basis of the carrying amount of each asset in the unit (group of units), considering

not

to reduce the carrying amount of the asset below the highest of its fair value less cost of disposal, its value in use or zero.

The value in use of each CGU is determined on the basis of the present value of net future cash flows which would be generated by such CGU. Tenaris uses cash flow projections for a

five

year period with a terminal value calculated based on perpetuity and appropriate discount rates.

For purposes of calculating the fair value less costs of disposal, Tenaris uses the estimated value of future cash flows that a market participant could generate from the corresponding CGU.

Management judgment is required to estimate discounted future cash flows. Actual cash flows and values could vary significantly from the forecasted future cash flows and related values derived using discounting techniques.

Non-financial assets other than goodwill that suffered an impairment are reviewed for possible reversal at each reporting date.

Other investments

Other investments consist primarily of investments in financial instruments and time deposits with a maturity of more than

three

months at the date of purchase.

Certain non-derivative financial assets that the Company has both the ability and the intention to hold to maturity have been categorized as held to maturity financial assets. They are carried at amortized cost and the results are recognized in

Financial Results

in the Consolidated Income Statement using the effective interest method. Held to maturity instruments with maturities greater than

months after the balance sheet date are included in the non-current assets.

All other investments in financial instruments and time deposits are categorized as financial assets “at fair value through profit or loss” because such investments are both (i) held for trading and (ii) designated as such upon initial recognition because they are managed and their performance is evaluated on a fair value basis. The results of these investments are recognized in

Financial Results

in the Consolidated Income Statement.

Purchases and sales of financial investments are recognized as of their settlement date.

The fair values of quoted investments are generally based on current bid prices. If the market for a financial investment is

not

active or the securities are

not

listed, Tenaris estimates the fair value by using standard valuation techniques (see Section III Financial Risk Management).

Inventories

Inventories are stated at the lower between cost and net realizable value. The cost of finished goods and goods in process is comprised of raw materials, direct labor, utilities, freights and other direct costs and related production overhead costs, and it excludes borrowing costs. Allocation of fixed production costs is based on the normal level of production capacity. Supplies and raw material cost is mainly based on FIFO method while goods in progress and finished goods cost is mainly based on specific historical production costs for each production order. Tenaris estimates net realizable value of inventories by grouping, where applicable, similar or related items. Net realizable value is the estimated selling price in the ordinary course of business, less any estimated costs of completion and selling expenses. Third parties goods in transit as of year-end are valued based on the supplier’s invoice cost.

Tenaris establishes an allowance for obsolete or slow-moving inventories related to finished goods, goods in process, supplies and spare parts. For slow moving or obsolete finished products, an allowance is established based on management’s analysis of product aging. An allowance for obsolete and slow-moving inventory of supplies and spare parts is established based on management's analysis of such items to be used as intended and the consideration of potential obsolescence due to technological changes, aging and consumption patterns.

Trade and other receivables

Trade and other receivables are recognized initially at fair value, generally the original invoice amount. Tenaris analyzes its trade receivables on a regular basis and, when aware of a specific counterparty’s difficulty or inability to meet its obligations, impairs any amounts due by means of a charge to an allowance for doubtful accounts. In addition, trade accounts receivable overdue by more than

180

days and which are

not

covered by a credit collateral, guarantee, insurance or similar surety, are provisioned.

Cash and cash equivalents

Cash and cash equivalents are comprised of cash at banks, liquidity funds and short-term investments with a maturity of less than

three

months at the date of purchase which are readily convertible to known amounts of cash. Assets recorded in cash and cash equivalents are carried at fair market value or at historical cost which approximates fair market value.

In the Consolidated Statement of Financial Position, bank overdrafts are included in

Borrowings

in current liabilities.

For the purposes of the Consolidated Statement of Cash Flows, cash and cash equivalents includes overdrafts.

Equity

(

)

Equity components

The Consolidated Statement of Changes in Equity includes:

The value of share capital, legal reserve, share premium and other distributable reserves calculated in accordance with Luxembourg law;

The currency translation adjustment, other reserves, retained earnings and non-controlling interest calculated in accordance with IFRS.

(

)

Share capital

The Company has an authorized share capital of a single class of

2.5

billion shares having a nominal value of

$1.00

per share. Total ordinary shares issued and outstanding as of

December 31, 2017,

2016

and

2015

are

1,180,536,830

with a par value of

1.00

per share with

one

vote each. All issued shares are fully paid.

(

)

Dividends distribution by the Company to shareholders

Dividends distributions are recorded in the Company’s financial statements when Company’s shareholders have the right to receive the payment, or when interim dividends are approved by the Board of Directors in accordance with the by-laws of the Company.

Dividends

may

be paid by the Company to the extent that it has distributable retained earnings, calculated in accordance with Luxembourg law (see Note

(iii)).

Borrowings

Borrowings are recognized initially at fair value net of transaction costs incurred and subsequently measured at amortized cost. Any difference between the proceeds (net of transaction costs) and the redemption amount is recognized in profit or loss over the period of the borrowings using the effective interest method.

Current and Deferred income tax

The income tax expense or credit for the period is the tax payable on the current period’s taxable income based on the applicable income tax rate for each jurisdiction adjusted by changes in deferred tax assets and liabilities attributable to temporary differences and to unused tax losses. Tax is recognized in the Consolidated Income Statement, except for tax items recognized in the Consolidated Statement of Other Comprehensive Income.

The current income tax charge is calculated on the basis of the tax laws enacted or substantively enacted at the reporting date in the countries where the Company’s subsidiaries operate and generate taxable income. Management periodically evaluates positions taken in tax returns with respect to situations in which applicable tax regulations are subject to interpretation and establishes provisions when appropriate.

Deferred income tax is recognized applying the liability method on temporary differences arising between the tax basis of assets and liabilities and their carrying amounts in the financial statements. The principal temporary differences arise from fair value adjustments of assets acquired in business combinations, the effect of currency translation on depreciable fixed assets and inventories, depreciation on property, plant and equipment, valuation of inventories and provisions for pension plans. Deferred tax assets are also recognized for net operating loss carry-forwards. Deferred tax assets and liabilities are measured at the tax rates that are expected to apply in the time period when the asset is realized or the liability is settled, based on tax laws that have been enacted or substantively enacted at the reporting date.

Deferred tax assets are recognized to the extent that it is probable that future taxable income will be available against which the temporary differences can be utilized. At the end of each reporting period, Tenaris reassesses unrecognized deferred tax assets. Tenaris recognizes a previously unrecognized deferred tax asset to the extent that it has become probable that future taxable income will allow the deferred tax asset to be recovered.

Deferred tax liabilities and assets are

not

recognized for temporary differences between the carrying amount and tax basis of investments in foreign operations where the company is able to control the timing of the reversal of the temporary differences and it is probable that the differences will

not

reverse in the foreseeable future.

Deferred tax assets and liabilities are offset when there is a legally enforceable right to offset current tax assets and liabilities and when the deferred tax balances relate to the same taxation authority. Current tax assets and tax liabilities are offset where the entity has a legally enforceable right to offset and intends either to settle on a net basis, or to realize the asset and settle the liability simultaneously.

Employee benefits

(

)

Short-term obligations

Liabilities for wages and salaries are recognized in respect of employees’ services up to the end of the reporting period and are measured at the amounts expected to be paid when the liabilities are settled. The liabilities are presented as current employee benefit obligations in the balance sheet.

(

)

Post employment benefits

The Company has defined benefit and defined contribution plans. A defined benefit plan is a pension plan that defines an amount of pension benefit that an employee will receive on retirement, usually dependent on

one

or more factors such as age, years of service and compensation.

The liability recognized in the statement of financial position in respect of defined benefit pension plans is the present value of the defined benefit obligation at the end of the reporting period less the fair value of plan assets, if any. The defined benefit obligation is calculated annually (at year end) by independent actuaries using the projected unit credit method. The present value of the defined benefit obligation is determined by discounting the estimated future cash outflows using interest rates of high-quality corporate bonds that are denominated in the currency in which the benefits will be paid, and that have terms to maturity approximating to the terms of the related pension obligation.

Remeasurement gains and losses arising from experience adjustments and changes in actuarial assumptions are charged or credited to equity in

Other comprehensive income

in the period in which they arise. Past-service costs are recognized immediately in the Income Statement.

For defined benefit plans, net interest income/expense is calculated based on the surplus or deficit derived by the difference between the defined benefit obligations less fair value of plan assets. For defined contribution plans, the Company pays contributions to publicly or privately administered pension insurance plans on a mandatory, contractual or voluntary basis. The Company has

further payment obligations once the contributions have been paid. The contributions are recognized as employee benefit expenses when they are due. Prepaid contributions are recognized as an asset to the extent that a cash refund or a reduction in the future payments is available.

Tenaris sponsors funded and unfunded defined benefit pension plans in certain subsidiaries. The most significant are:

An unfunded defined benefit employee retirement plan for certain senior officers. The plan is designed to provide certain benefits to those officers (additional to those contemplated under applicable labor laws) in case of termination of the employment relationship due to certain specified events, including retirement. This unfunded plan provides defined benefits based on years of service and final average salary. As of

December 31, 2017

the outstanding liability for this plan amounts to

$46.8

million.

Employees’ service rescission indemnity: the cost of this obligation is charged to the Consolidated Income Statement over the expected service lives of employees. This provision is primarily related to the liability accrued for employees at Tenaris’s Italian subsidiary. As from

January 1, 2007

as a consequence of a change in an Italian law, employees were entitled to make contributions to external funds, thus, Tenaris’s Italian subsidiary pays every year the required contribution to the funds with

further obligation. As a result, the plan changed from a defined benefit plan to a defined contribution plan effective from that date, but only limited to the contributions of

2007

onwards. As of

December 31, 2017

the outstanding liability for this plan amounts to

$19.3

million.

Funded retirement benefit plans held in Canada for salary and hourly employees hired prior a certain date based on years of service and, in the case of salaried employees, final average salary. Plan assets consist primarily of investments in equities and money market funds. Both plans were replaced for defined contribution plans. Effective

June 2016

the salary plan was frozen for the purposes of credited service as well as determination of final average pay. As of

December 31, 2017

the outstanding liability for this plan amounts to

$16.7

million.

Funded retirement benefit plan held in the US for the benefit of some employees hired prior a certain date, frozen for the purposes of credited service as well as determination of final average pay for the retirement benefit calculation. Plan assets consist primarily of investments in equities and money market funds. Additionally, an unfunded postretirement health and life plan is present that offers limited medical and life insurance benefits to the retirees, hired before a certain date. As of

December 31, 2017

the outstanding liability for this plan amounts to

$12.3

million.

(

)

Other long term benefits

During

2007,

Tenaris launched an employee retention and long term incentive program (the “Program”) applicable to certain senior officers and employees of the Company, who will be granted a number of Units throughout the duration of the Program. The value of each of these Units is based on Tenaris’s shareholders’ equity (excluding non-controlling interest). Also, the beneficiaries of the Program are entitled to receive cash amounts based on (i) the amount of dividend payments made by Tenaris to its shareholders, and (ii) the number of Units held by each beneficiary to the Program. Units vest ratably over a period of

four

years and will be mandatorily redeemed by the Company

ten

years after grant date, with the option of an early redemption at

seven

years after the grant date. As the cash payment of the benefit is tied to the book value of the shares, and

not

to their market value, Tenaris valued this long-term incentive program as a long term benefit plan as classified in IAS

“Employee Benefits”.

As of

December 31, 2017

and

2016,

the outstanding liability corresponding to the Program amounts to

$79.2

million and

$78.7

million, respectively. The total value of the units granted (vested and unvested) to date under the program, considering the number of units and the book value per share as of

December 31, 2017

and

2016,

$94.8

million and

$92.9

million, respectively.

(

)

Termination benefits

Terminations benefits are payable when employment is terminated by Tenaris before the normal retirement date, or when an employee accepts voluntary redundancy in exchange for these benefits. Tenaris recognizes termination benefits at the earlier of the following dates: (a) when it can

longer withdraw the offer of those benefits; and (b) when the costs for a restructuring that is within the scope of IAS

and involves the payment of terminations benefits. In the case of an offer made to encourage voluntary redundancy, the termination benefits are measured based on the number of employees expected to accept the offer.

(

)

Other compensation obligations

Employee entitlements to annual leave and long-service leave are accrued as earned.

Compensation to employees in the event of dismissal is charged to income in the year in which it becomes payable.

Provisions

Tenaris is subject to various claims, lawsuits and other legal proceedings, including customer claims, in which a

third

party is seeking payment for alleged damages, reimbursement for losses or indemnity. Tenaris’s potential liability with respect to such claims, lawsuits and other legal proceedings cannot be estimated with certainty. Management periodically reviews the status of each significant matter and assesses potential financial exposure. If, as a result of past events, a potential loss from a claim or proceeding is considered probable and the amount can be reliably estimated, a provision is recorded. Accruals for loss contingencies reflect a reasonable estimate of the losses to be incurred based on information available to management as of the date of preparation of the financial statements, and take into consideration Tenaris’s litigation and settlement strategies. These estimates are primarily constructed with the assistance of legal counsel. As the scope of liabilities become better defined, there

may

be changes in the estimates of future costs which could have a material adverse effect on its results of operations, financial condition and cash flows.

If Tenaris expects to be reimbursed for an accrued expense, as would be the case for an expense or loss covered under an insurance contract, and reimbursement is considered virtually certain, the expected reimbursement is recognized as a receivable.

This note should be read in conjunction with Note

25.

Trade and other payables

Trade and other payables are recognized initially at fair value, generally the nominal invoice amount and subsequently measured at amortised cost. They are presented as current liabilities unless payment is

not

due within

months after the reporting period.

Revenue recognition

Revenue comprises the fair value of the consideration received or receivable for the sale of goods and services in the ordinary course of Tenaris’s activities. Revenue is shown net of value-added tax, returns, rebates and discounts and after eliminating sales within the group.

Tenaris’s products and services are sold based upon purchase orders, contracts or upon other persuasive evidence of an arrangement with customers, including that the sales price is known or determinable. Sales are recognized as revenue upon delivery, when neither continuing managerial involvement nor effective control over the products is retained by Tenaris and when collection is reasonably assured. Delivery is defined by the transfer of risk and

may

include delivery to a storage facility located at

one

of the Company’s subsidiaries. For bill and hold transactions revenue is recognized only to the extent (a) it is highly probable delivery will be made; (b) the products have been specifically identified and are ready for delivery; (c) the sales contract specifically acknowledges the deferred delivery instructions; (d) the usual payment terms apply.

The percentage of total sales that were generated from bill and hold arrangements for products located in Tenaris’s storage facilities that have

not

been shipped to customers amounted to

3.3%,

2.8%

and

3.0%

as of

December 31, 2017,

2016

and

2015,

respectively. The Company has

not

experienced any material claims requesting the cancellation of bill and hold transactions.

Other revenues earned by Tenaris are recognized on the following basis:

Construction contracts (mainly applicable to Tenaris Brazilian subsidiaries and amounted to

$11

million,

0.21%

of total sales). The revenue recognition of the contracts follows the IAS

”Construction Contracts" guidance, that means, when the outcome of a construction contract can be estimated reliably and it is probable that the contract will be profitable, contract revenue is recognized over the period of the contract by reference to the stage of completion (measured by reference to the contract costs incurred up to the end of the reporting period as a percentage of total estimated costs for each contract).

Interest income: on the effective yield basis.

Dividend income from investments in other companies: when Tenaris’s right to receive payment is established.

Cost of sales and other selling expenses

Cost of sales and other selling expenses are recognized in the Consolidated Income Statement on the accrual basis of accounting.

Commissions, freights and other selling expenses, including shipping and handling costs, are recorded in

Selling, general and administrative expenses

in the Consolidated Income Statement.

Earnings per share

Earnings per share are calculated by dividing the income attributable to owners of the parent by the daily weighted average number of common shares outstanding during the year.

There are

dilutive potential ordinary shares.

Financial instruments

Non derivative financial instruments comprise investments in financial debt instruments and equity, time deposits, trade and other receivables, cash and cash equivalents, borrowings and trade and other payables. Tenaris’s non derivative financial instruments are classified into the following categories:

Financial instruments at fair value through profit and loss: comprise mainly Other Investments current, investments in certain financial debt instruments and time deposits held for trading expiring in less than

ninety

days from the measurement date (included within cash and cash equivalents).

Loans and receivables: comprise cash and cash equivalents, trade receivables and other receivables and are measured at amortized cost using the effective interest rate method less any impairment.

Available for sale assets: comprise the Company’s interest in the Venezuelan Companies (see Note

Held to maturity: comprise financial assets that the Company has both the ability and the intention to hold to maturity. They are measured at amortized cost using the effective interest method.

Other financial liabilities: comprise borrowings, trade and other payables and are measured at amortized cost using the effective interest rate method.

The classification depends on the nature and purpose that the Company sets to the financial instrument.

Financial assets and liabilities are recognized and derecognized on their settlement date.

Accounting for derivative financial instruments and hedging activities is included within the Section III, Financial Risk Management.

Non-current assets held for sale and discontinued operations

Non-current assets (or disposal groups) are classified as held for sale if their carrying amount will be recovered principally through a sale transaction rather than through continuing use and a sale is considered highly probable. They are measured at the lower of their carrying amount and fair value less costs to sell, except for assets such as deferred tax assets, assets arising from employee benefits and financial assets that are carried at fair value.

An impairment loss is recognized for any initial or subsequent write-down of the asset (or disposal group) to fair value less costs to sell. A gain is recognized for any subsequent increases in fair value less costs to sell of an asset (or disposal group), but

not

in excess of any cumulative impairment loss previously recognized.

Non-current assets (including those that are part of a disposal group) are

not

depreciated or amortized while they are classified as held for sale. Interest and other expenses attributable to the liabilities of a disposal group classified as held for sale continue to be recognized.

Non-current assets classified as held for sale and the assets of a disposal group classified as held for sale are presented separately from the other assets in the balance sheet. The liabilities of a disposal group classified as held for sale are presented separately from other liabilities in the balance sheet.

A discontinued operation is a component of the entity that has been disposed of or is classified as held for sale and that represents a separate line of business or geographical area of operations, is part of a single coordinated plan to dispose of such a line of business or area of operations, or is a subsidiary acquired exclusively with a view to resale. The results of discontinued operations are presented separately in the Consolidated Income Statement. See Note

28.

Financial Risk Management

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of financial instruments [text block]

iii. Financial risk management

The multinational nature of Tenaris’s operations and customer base exposes the Company to a variety of risks, mainly related to market risks (including the effects of changes in foreign currency exchange rates and interest rates), credit risk and capital market risk. In order to manage the volatility related to these exposures, management evaluates exposures on a consolidated basis, taking advantage of exposure netting. The Company or its subsidiaries

may

then enter into various derivative transactions in order to prevent potential adverse impacts on Tenaris’s financial performance. Such derivative transactions are executed in accordance with internal policies and hedging practices.

A. Financial Risk Factors

(i)

Capital Risk Management

Tenaris seeks to maintain a low debt to total equity ratio considering the industry and the markets where it operates. The year-end ratio of debt to total equity (where “debt” comprises financial borrowings and “total equity” is the sum of financial borrowings and equity) is

0.08

as of

December 31, 2017

and

0.07

as of

December 31, 2016.

The Company does

not

have to comply with regulatory capital adequacy requirements.

(ii)

Foreign exchange risk

Tenaris manufactures and sells its products in a number of countries throughout the world and consequently is exposed to foreign exchange rate risk. Since the Company’s functional currency is the U.S. dollar the purpose of Tenaris’s foreign currency hedging program is mainly to reduce the risk caused by changes in the exchange rates of other currencies against the U.S. dollar.

Tenaris’s exposure to currency fluctuations is reviewed on a periodic consolidated basis. A number of derivative transactions are performed in order to achieve an efficient coverage in the absence of operative or natural hedges. Almost all of these transactions are forward exchange rates contracts (see Note

Derivative financial instruments).

Tenaris does

not

enter into derivative financial instruments for trading or other speculative purposes, other than non-material investments in structured products.

In the case of subsidiaries with functional currencies other than the U.S. dollar, the results of hedging activities, reported in accordance with IFRS,

may

not

reflect entirely the management’s assessment of its foreign exchange risk hedging program. Intercompany balances between Tenaris’s subsidiaries

may

generate financial gains (losses) to the extent that functional currencies differ.

The value of Tenaris’s financial assets and liabilities is subject to changes arising from the variation of foreign currency exchange rates. The following table provides a breakdown of Tenaris’s main financial assets and liabilities (including foreign exchange derivative contracts) which impact the Company’s profit and loss as of

December 31, 2017

and

2016:

All amounts Long / (Short) in thousands of U.S. dollars	As of December 31,
Currency Exposure / Functional currency	2017			2016
Argentine Peso / U.S. Dollar		(64,482	)		(60,204	)
Euro / U.S. Dollar		(365,926	)		(406,814	)
U.S. Dollar / Brazilian Real		(183	)		125,880

The main relevant exposures correspond to:

Argentine Peso / U.S. dollar

As of

December 31, 2017

and

2016

consisting primarily of Argentine Peso-denominated financial, trade, social and fiscal payables at certain Argentine

subsidiaries whose functional currency is the U.S. dollar. A change of

in the ARS/USD exchange rate would have generated a pre-tax gain / loss of

0.6

million as of

December 31, 2017

and

2016.

Euro / U.S. dollar

As of

December 31, 2017

and

2016,

consisting primarily of Euro-denominated intercompany liabilities at certain subsidiaries

whose

functional currency is the U.S. dollar. A change of

in the EUR/USD exchange rate would have generated a pre-tax gain / loss of

$3.7

million and

$4.1

million as of

December 31, 2017

and

2016,

respectively, which would have been to a large extent offset by changes in currency translation adjustment included in Tenaris’s net equity position.

U.S. dollar / Brazilian Real

As of

December 31, 2016

consisting primarily of Cash and cash equivalent and Other investments denominated in U.S. dollar at subsidiaries

whose

functional currency is the Brazilian real. A change of

in the BRL/USD exchange rate would generate a pre-tax gain / loss of

$1.3

million in

December 31, 2016 (

including a gain / loss of

$0.5

million in

2016

due to foreign exchange derivative contracts entered to preserve the U.S. dollar value of trade receivables and cash denominated in Brazilian Real), which would have been to a large extent offset by changes in currency translation adjustment included in Tenaris’s net equity position.

Considering the balances held as of

December 31, 2017

on financial assets and liabilities exposed to foreign exchange rate fluctuations, Tenaris estimates that the impact of a simultaneous

appreciation / depreciation movement in the levels of foreign currencies exchange rates relative to the U.S. dollar, would be a pre-tax gain / loss of

$5.3

million (including a loss / gain of

$6.7

million due to foreign exchange derivative contracts), which would be partially offset by changes to Tenaris’s net equity position of

$3.4

million. For balances held as of

December 31, 2016,

a simultaneous

favorable / unfavorable movement in the foreign currencies exchange rates relative to the U.S. dollar, would have generated a pre-tax gain / loss of

$6.6

million (including a loss / gain of

$4.0

million due to foreign exchange derivative contracts), which would have been partially offset by changes to Tenaris’s net equity position of

$4.2

million.

(iii) Interest rate risk

Tenaris is subject to interest rate risk on its investment portfolio and its debt. The Company uses a mix of variable and fixed rate debt in combination with its investment portfolio strategy. From time to time, the Company

may

choose to enter into

foreign exchange derivative contracts and / or

interest rate swaps to mitigate the exposure to changes in the interest rates.

The following table summarizes the proportions of variable-rate and fixed-rate debt as of each year end.

	As of December 31,
	2017					2016
	Amount in thousands of U.S. dollars		%			Amount in thousands of U.S. dollars		%
Fixed rate (*)		946,215		98	%		820,600		98	%
Variable rate		19,644		2	%		19,636		2	%
Total		965,859					840,236

(*)

Out of the

$946

Million fixed rate borrowings

$913

Million are short-term.

The Company estimates that, if market interest rates applicable to Tenaris’s borrowings had been

100

basis points higher, then the additional pre-tax loss would have been

$8.0

million in

2017

and

$8.8

million in

2016.

(iv)

Credit risk

Credit risk arises from cash and cash equivalents, deposits with banks and financial institutions, as well as credit exposures to customers, including outstanding receivables and committed transactions. The Company also actively monitors the creditworthiness of its treasury, derivative and insurance counterparties in order to minimize its credit risk.

There is

significant concentration of credit risk from customers.

single customer comprised more than

10%

of Tenaris’s net sales in

2017,

2016

and

2015.

Tenaris’s credit policies related to sales of products and services are designed to identify customers with acceptable credit history and to allow Tenaris to require the use of credit insurance, letters of credit and other instruments designed to minimize credit risks

whenever deemed necessary. Tenaris maintains allowances for impairment for potential credit losses

(See Section II J).

As of

December 31, 2017

and

2016

trade receivables amount to

$1,214.1

million and

$954.7

million respectively. Trade receivables have guarantees under credit insurance of

$190.7

million and

$222.1

million, letter of credit and other bank guarantees of

$42.2

million and

$117.8

million, and other guarantees of

$14.1

million and

$15.6

million as of

December 31, 2017

and

2016

respectively.

As of

December 31, 2017

and

2016

past due trade receivables amounted to

$230.9

million and

$249.0

million, respectively. Out of those amounts

$27.3

million and

$83.1

million are guaranteed trade receivables while

$78.4

million and

$85.7

million are included in the allowance for doubtful accounts. Both the allowance for doubtful accounts and the existing guarantees are sufficient to cover doubtful trade receivables.

(v)

Counterparty risk

Tenaris has investment guidelines with specific parameters to limit issuer risk on marketable securities. Counterparties for derivatives and cash transactions are limited to high credit quality financial institutions, normally investment grade.

Approximately

71%

of Tenaris’s liquid financial assets correspond to Investment Grade-rated instruments as of

December 31, 2017,

in comparison with approximately

82%

as of

December 31, 2016.

(vi)

Liquidity risk

Tenaris financing strategy aims to maintain adequate financial resources and access to additional liquidity. During

2017,

Tenaris has counted on cash flows from operations as well as additional bank financing to fund its transactions.

Management maintains sufficient cash and marketable securities to finance normal operations and believes that Tenaris also has appropriate access to market for short-term working capital needs.

Liquid financial assets as a whole (comprising cash and cash equivalents and other investments) were

11%

of total assets at the end of

2017

compared to

16%

at the end of

2016.

Tenaris has a conservative approach to the management of its liquidity, which consists of i) cash and cash equivalents (cash in banks, liquidity funds and investments with a maturity of less than

three

months at the date of purchase), and ii) Other Investments (fixed income securities, time deposits, and fund investments).

Tenaris holds primarily investments in money market funds and variable or fixed-rate securities from investment grade issuers. As of

December 31, 2017

and

2016,

Tenaris does

not

have direct exposure to financial instruments issued by European sovereign counterparties.

Tenaris holds its investments primarily in U.S. dollars. As of

December 31, 2017

and

2016,

U.S. dollar denominated liquid assets represented approximately

93%

and

95%

of total liquid financial assets respectively.

(vii)

Commodity price risk

In the ordinary course of its operations, Tenaris purchases commodities and raw materials that are subject to price volatility caused by supply conditions, political and economic variables and other factors. As a consequence, Tenaris is exposed to risk resulting from fluctuations in the prices of these commodities and raw materials. Tenaris fixes the prices of such raw materials and commodities for short-term periods, typically

not

in excess of

one

year, in general Tenaris does

not

hedge this risk.

B. Category of Financial Instruments and Classification Within the Fair Value Hierarchy

Accounting policies for financial instruments have been applied to classify as either: loans and receivables, held-to-maturity, available-for-sale, or fair value through profit and loss. For financial instruments that are measured in the statement of financial position at fair value, IFRS

requires a disclosure of fair value measurements by level according to the following fair value measurement hierarchy:

Level

- Quoted prices (unadjusted) in active markets for identical assets or liabilities.

Level

- Inputs other than quoted prices included within Level

that are observable for the asset or liability, either directly (that is, as prices) or indirectly (that is, derived from prices).

Level

- Inputs for the asset or liability that are

not

based on observable market data (that is, unobservable inputs).

The following tables present the financial instruments by category and levels as of

December 31, 2017

and

2016.

			Measurement Categories								At Fair Value
December 31, 2017	Carrying Amount		Loans & Receivables		Held to Maturity		Available for sale		Fair value through profit and loss		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents		330,221		150,948		-		-		179,273		179,273		-		-
Cash at banks		150,948		150,948		-		-		-		-		-		-
Liquidity funds		66,033		-		-		-		66,033		66,033		-		-
Short – term investments		113,240		-		-		-		113,240		113,240		-		-
Other investments		1,192,306		-		220,838		-		971,468		459,476		511,992		-
Fixed income (time-deposit, zero coupon bonds, commercial papers)		437,406		-		-		-		437,406		9,943		427,463		-
Certificates of deposits		297,788		-		-		-		297,788		-		297,788		-
Commercial papers		9,943		-		-		-		9,943		9,943		-		-
Other notes		129,675		-		-		-		129,675		-		129,675		-
Bonds and other fixed income		754,800		-		220,838		-		533,962		449,533		84,429		-
U.S. government securities		130,477		-		-		-		130,477		130,477		-		-
Non - U.S. government securities		161,063		-		36,283		-		124,780		124,780		-		-
Corporates securities		378,831		-		184,555		-		194,276		194,276		-		-
Structured notes		68,044		-		-		-		68,044		-		68,044		-
Mortgage and asset-backed securities		16,385		-		-		-		16,385		-		16,385		-
Others		100		-		-		-		100		-		100		-
Other Investments Non- current		128,335		-		123,498		-		4,837		-		-		4,837
Bonds and other fixed income		123,498		-		123,498		-		-		-		-		-
Other investments		4,837		-		-		-		4,837		-		-		4,837
Trade receivables		1,214,060		1,214,060		-		-		-		-		-		-
Receivables C and NC		327,258		176,716		-		-		8,230		-		8,230		-
Foreign exchange derivatives contracts		8,230		-		-		-		8,230		-		8,230		-
Other receivables		176,716		176,716		-		-		-		-		-		-
Other receivables (non-financial)		142,314		-		-		-		-		-		-		-
Available for sale assets (*)		21,572		-		-		21,572		-		-		-		21,572
Total				1,541,724		344,336		21,572		1,163,808		638,749		520,222		26,409
Liabilities
Borrowings C and NC		965,859		965,859		-		-		-		-		-		-
Trade payables		750,739		750,739		-		-		-		-		-		-
Other liabilities		197,504		-		-		-		39,799		-		39,799		-
Foreign exchange derivatives contracts		39,799		-		-		-		39,799		-		39,799		-
Other liabilities (non-financial)		157,705		-		-		-		-		-		-		-
Total				1,716,598		-		-		39,799		-		39,799		-

			Measurement Categories								At Fair Value
December 31, 2016	Carrying Amount		Loans & Receivables		Held to Maturity		Available for sale		Fair value through profit and loss		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents		399,737		92,730		-		-		307,007		307,007		-		-
Cash at banks		92,730		92,730		-		-		-		-		-		-
Liquidity funds		215,807		-		-		-		215,807		215,807		-		-
Short – term investments		91,200		-		-		-		91,200		91,200		-		-
Other investments Current		1,633,142		-		246,031		-		1,387,111		607,866		779,245		-
Fixed income (time-deposit, zero cupon bonds, commercial papers)		782,029		-		-		-		782,029		76,260		705,769		-
Non - U.S. sovereign bills		41,370		-		-		-		41,370		41,370		-		-
Certificates of deposits		525,068		-		-		-		525,068		-		525,068		-
Commercial papers		34,890		-		-		-		34,890		34,890		-		-
Other notes		180,701		-		-		-		180,701		-		180,701		-
Bonds and other fixed income		841,638		-		246,031		-		595,607		522,131		73,476		-
U.S. government securities		216,732		-		-		-		216,732		216,732		-		-
Non - U.S. government securities		88,805		-		32,644		-		56,161		56,161		-		-
Corporates securities		462,625		-		213,387		-		249,238		249,238		-		-
Mortgage and asset-backed securities		73,476		-		-		-		73,476		-		73,476		-
Fund investments		9,475		-		-		-		9,475		9,475		-		-
Other Investments Non- current		249,719		-		248,049		-		1,670		-		-		1,670
Bonds and other fixed income		248,049		-		248,049		-		-		-		-		-
Other investments		1,670		-		-		-		1,670		-		-		1,670
Trade receivables		954,685		954,685		-		-		-		-		-		-
Receivables C and NC		321,718		176,990		-		-		2,759		-		2,759		-
Foreign exchange derivatives contracts		2,759		-		-		-		2,759		-		2,759		-
Other receivables		176,990		176,990		-		-		-		-		-		-
Other receivables (non-financial)		141,969		-		-		-		-		-		-		-
Available for sale assets (*)		21,572		-		-		21,572		-		-		-		21,572
Total				1,224,405		494,080		21,572		1,698,547		914,873		782,004		23,242
Liabilities
Borrowings C and NC		840,236		840,236		-		-		-		-		-		-
Trade payables		556,834		556,834		-		-		-		-		-		-
Other liabilities		183,887		-		-		-		42,635		-		42,635		-
Foreign exchange derivatives contracts		42,635		-		-		-		42,635		-		42,635		-
Other liabilities (non-financial)		141,252		-		-		-		-		-		-		-
Total				1,397,070		-		-		42,635		-		42,635		-

(*) For further detail regarding Available for sale assets, see Note

31.

There were

transfers between Levels during the year

The fair value of financial instruments traded in active markets is based on quoted market prices at the reporting date. A market is regarded as active if quoted prices are readily and regularly available from an exchange, dealer, broker, industry group, pricing service, or regulatory agency, and those prices represent actual and regularly occurring market transactions on an arm’s length basis. The quoted market price used for financial assets held by Tenaris is the current bid price. These instruments are included in Level

and comprise primarily corporate and sovereign debt securities.

The fair value of financial instruments that are

not

traded in an active market (such as certain debt securities, certificates of deposits with original maturity of more than

three

months, forward and interest rate derivative instruments) is determined by using valuation techniques which maximize the use of observable market data when available and rely as little as possible on entity specific estimates. If all significant inputs required to value an instrument are observable, the instrument is included in Level

Tenaris values its assets and liabilities included in this level using bid prices, interest rate curves, broker quotations, current exchange rates, forward rates and implied volatilities obtained from market contributors as of the valuation date.

one

or more of the significant inputs are

not

based on observable market data, the instruments are included in Level

Tenaris values its assets and liabilities in this level using observable market inputs and management assumptions which reflect the Company’s best estimate on how market participants would price the asset or liability at measurement date. Main balances included in this level correspond to Available for sale assets related to Tenaris’s interest in Venezuelan companies under process of nationalization (see Note

The following table presents the changes in Level

assets and liabilities:

	Year ended December 31,
	2017			2016
	Assets / Liabilities
At the beginning of the year		23,242			23,234
Acquisition		3,681			-
Decrease due to write down		(564	)		-
Currency translation adjustment and others		50			8
At the end of the year		26,409			23,242

C. Fair value estimation

Financial assets or liabilities classified at fair value through profit or loss are measured under the framework established by the IASB accounting guidance for fair value measurements and disclosures.

The fair values of quoted investments are generally based on current bid prices. If the market for a financial asset is

not

active or

market is available, fair values are established using standard valuation techniques.

Some of Tenaris’s investments are designated as held to maturity and measured at amortized cost. Tenaris estimates that the fair value of these financial assets is

100.9%

and

100.8%

of its carrying amount including interests accrued as of

December 31, 2017

and

2016

respectively.

The fair value of all outstanding derivatives is determined using specific pricing models that include inputs that are observable in the market or can be derived from or corroborated by observable data. The fair value of forward foreign exchange contracts is calculated as the net present value of the estimated future cash flows in each currency, based on observable yield curves, converted into U.S. dollars at the spot rate of the valuation date.

Borrowings are comprised primarily of fixed rate debt and variable rate debt with a short term portion where interest has already been fixed. They are classified under other financial liabilities and measured at their amortized cost. Tenaris estimates that the fair value of its main financial liabilities is approximately

99.4%

of its carrying amount including interests accrued in

2017

as compared with

99.7%

2016.

Fair values were calculated using standard valuation techniques for floating rate instruments and comparable market rates for discounting flows.

D. Accounting for derivative financial instruments and hedging activities

Derivative financial instruments are initially recognized in the statement of financial position at fair value through profit and loss on each date a derivative contract is entered into and are subsequently remeasured at fair value. Specific tools are used for calculation of each instrument’s fair value and these tools are tested for consistency on a monthly basis. Market rates are used for all pricing operations. These include exchange rates, deposit rates and other discount rates matching the nature of each underlying risk.

As a general rule, Tenaris recognizes the full amount related to the change in fair value of derivative financial instruments in

Financial Results

in the Consolidated Income Statement.

Tenaris designates certain derivatives as hedges of particular risks associated with recognized assets or liabilities or highly probable forecast transactions. These transactions (mainly currency forward contracts on highly probable forecast transactions) are classified as cash flow hedges. The effective portion of the fair value of derivatives that are designated and qualify as cash flow hedges is recognized in equity. Amounts accumulated in equity are then recognized in the income statement in the same period as the offsetting losses and gains on the hedged item. The gain or loss relating to the ineffective portion is recognized immediately in the income statement. The fair value of Tenaris’s derivative financial instruments (assets or liabilities) continues to be reflected in the statement of financial position. The full fair value of a hedging derivative is classified as a current or non-current asset or liability according to its expiry date.

For transactions designated and qualifying for hedge accounting, Tenaris documents at the inception of the transaction the relationship between hedging instruments and hedged items, as well as its risk management objectives and strategy for undertaking various hedge transactions. Tenaris also documents its assessment on an ongoing basis, of whether the derivatives that are used in hedging transactions are highly effective in offsetting changes in the fair value or cash flow of hedged items. At

December 31, 2017

and

2016,

the effective portion of designated cash flow hedges which is included in “

Other Reserves”

in equity amounts to

$0.2

million debit and

$4.7

million credit respectively (see Note

Derivative financial instruments

The fair values of various derivative instruments used for hedging purposes are disclosed in Note

24.

Movements in the hedging reserve included within “

Other Reserves”

in equity are also shown in Note

24.

Note 1 - Segment Information

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of entity's operating segments [text block]

Segment information

As mentioned in section II. AP – C, the Segment Information is disclosed as follows:

Reportable operating segments

(All amounts in million US dollar)

Year ended December 31, 2017	Tubes			Other			Continuing operations			Discontinued operations
IFRS - Net Sales		4,966			323			5,289			12
Management view - operating income		115			48			163			3
Difference in cost of sales		164			1			165			(1	)
Direct cost and others		115			-			115			(1	)
Absorption		49			1			50			-
Differences in depreciation and amortization		(3	)		-			(3	)		-
Differences in selling, general and administrative expenses		14			(6	)		8			-
Differences in other operating income (expenses), net		2			-			2			-
IFRS - operating income		292			43			335			2
Financial income (expense), net								(23	)		-
Income before equity in earnings of non-consolidated companies and income tax								312			2
Equity in earnings of non-consolidated companies								116			-
Income before income tax								428			2
Capital expenditures		550			8			558			-
Depreciation and amortization		594			15			609			-

Year Ended December 31, 2016	Tubes			Other			Continuing operations			Discontinued operations
IFRS - Net Sales		4,015			278			4,294			235
Management view - operating income		19			19			38			62
Difference in cost of sales		(108	)		(8	)		(116	)		4
Direct cost and others		(114	)		(8	)		(122	)		4
Absorption		6			-			6			-
Differences in Depreciation and Amortization		28			-			28			-
Differences in Selling, general and administrative expenses		(5	)		1			(4	)		-
Differences in Other operating income (expenses), net		(5	)		-			(5	)		-
IFRS - operating (loss) income		(71	)		12			(59	)		66
Financial income (expense), net								22			-
(Loss) income before equity in earnings of non-consolidated companies and income tax								(37	)		66
Equity in earnings of non-consolidated companies								71			-
Income before income tax								34			66
Capital expenditures		752			33			785			2
Depreciation and amortization		643			14			657			5

Year Ended December 31, 2015	Tubes			Other		Continuing operations			Discontinued operations
IFRS - Net Sales		6,444			459		6,903			198
Management view - operating income		686			27		713			39
Difference in cost of sales		(225	)		-		(225	)		(9	)
Direct cost and others		(184	)		-		(184	)		(9	)
Absorption		(41	)		-		(41	)		-
Differences in Depreciation and Amortization		(319	)		1		(318	)		-
Differences in Selling, general and administrative expenses		(4	)		-		(4	)		-
Differences in Other operating income (expenses), net		-			-		-			-
IFRS - operating income		138			28		166			30
Financial income (expense), net							15			-
Income before equity in earnings of non-consolidated companies and income tax							181			30
Equity in losses of non-consolidated companies							(40	)		-
Income before income tax							141			30
Capital expenditures		1,089			41		1,130			1
Depreciation and amortization		638			15		653			5

Transactions between segments, which were eliminated in consolidation, are mainly related to sales of scrap, energy, surplus raw materials and others from the Other segment to the Tubes segment for

$53,

$47

and

$57

million in

2017,

2016

and

2015,

respectively.

In addition to the amounts reconciled above, the main differences in net income arise from the impact of functional currencies on financial result, deferred income taxes as well as the result of investment in non-consolidated companies and changes on the valuation of inventories according to cost estimation internally defined.

Geographical information

(all amounts in thousands of U.S. dollars)	North America		South America		Europe		Middle East & Africa		Asia Pacific		Unallocated (*)		Total continuing operations		Total discontinued operations
Year ended December 31, 2017
Net sales		2,451,357		1,142,142		545,777		937,439		211,789		-		5,288,504		11,899
Total assets		7,925,520		2,975,599		2,002,658		391,029		441,546		661,866		14,398,218		-
Trade receivables		582,204		234,877		214,944		135,524		46,511		-		1,214,060		-
Property, plant and equipment, net		3,914,229		1,190,145		878,788		102,481		143,500		-		6,229,143		-
Capital expenditures		430,143		58,949		57,285		7,562		4,153		-		558,092		145
Depreciation and amortization		354,091		126,273		93,900		12,094		22,282		-		608,640		-

Year ended December 31, 2016
Net sales		1,320,297		1,210,527		565,173		1,055,994		141,601		-		4,293,592		234,911
Total assets		7,467,842		2,803,848		1,925,784		593,649		482,132		578,603		13,851,858		151,417
Trade receivables		229,390		204,746		161,291		308,919		50,339		-		954,685		33,620
Property, plant and equipment, net		3,652,032		1,237,391		847,318		106,941		158,257		-		6,001,939		41,470
Capital expenditures		646,545		59,780		35,270		24,166		19,201		-		784,962		1,911
Depreciation and amortization		381,811		128,458		113,875		11,053		21,912		-		657,109		5,303

Year ended December 31, 2015
Net sales		2,668,724		2,132,221		728,815		1,096,688		276,675		-		6,903,123		197,630
Total assets		8,625,806		2,931,297		1,877,429		429,317		423,479		512,217		14,799,545		87,429
Trade receivables		339,499		396,834		181,084		137,278		52,494		-		1,107,189		27,940
Property, plant and equipment, net		3,207,661		1,269,995		907,466		86,181		155,299		-		5,626,602		45,656
Capital expenditures		822,396		168,140		82,344		36,867		20,566		-		1,130,313		1,206
Depreciation and amortization		385,189		125,754		112,742		9,912		19,716		-		653,313		5,465

There are

revenues from external customers attributable to the Company’s country of incorporation (Luxembourg). For geographical information purposes, “North America” comprises Canada, Mexico and the USA (

31.8%

); “South America” comprises principally Argentina (

14.0%

), Brazil and Colombia; “Europe” comprises principally Italy and Romania; “Middle East and Africa” comprises principally Kazakhstan, United Arab Emirates, Nigeria and Saudi Arabia and; “Asia Pacific” comprises principally China, Japan and Thailand.

(*) Includes Investments in non-consolidated companies and Available for sale assets for

21.6

million in

2017,

2016

and

2015

(see Note

and

Note 2 - Cost of Sales

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of cost of sales [text block]

Cost of sales

	Year ended December 31,
(all amounts in thousands of U.S. dollars)	2017			2016			2015

Inventories at the beginning of the year		1,563,889			1,843,467			2,779,869

Plus: Charges of the year
Raw materials, energy, consumables and other		2,794,503			1,528,532			1,934,209
Services and fees		244,035			199,210			298,470
Labor cost		778,408			658,975			947,997
Depreciation of property, plant and equipment		383,490			376,965			377,596
Amortization of intangible assets		18,621			27,244			24,100
Maintenance expenses		183,370			122,553			184,053
Allowance for obsolescence		(12,917	)		32,765			68,669
Taxes		18,542			16,693			21,523
Other		88,823			89,575			92,059
		4,496,875			3,052,512			3,948,676
Less: Inventories at the end of the year (*)		(2,368,304	)		(1,593,708	)		(1,843,467	)
From discontinued operations		(7,403	)		(136,587	)		(137,318	)
		3,685,057			3,165,684			4,747,760

(*) Inventories as of

December 31, 2016

include $

29.8

million related to discontinued operations.

Note 3 - Selling, General and Administrative Expenses

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of general and administrative expense [text block]

Selling, general and administrative expenses

	Year ended December 31,
(all amounts in thousands of U.S. dollars)	2017			2016			2015

Services and fees		132,301			123,653			158,541
Labor cost		443,338			441,355			579,360
Depreciation of property, plant and equipment		17,979			16,965			18,543
Amortization of intangible assets		188,550			241,238			238,539
Commissions, freight and other selling expenses		339,759			243,401			351,657
Provisions for contingencies		17,664			30,841			19,672
Allowances for doubtful accounts		(5,421	)		(12,573	)		36,788
Taxes		56,826			67,724			129,018
Other		81,061			76,563			92,157
		1,272,057			1,229,167			1,624,275
From discontinued operations		(2,041	)		(32,238	)		(30,678	)
		1,270,016			1,196,929			1,593,597

Note 4 - Labor Costs - Labor Costs (Included in Cost of Sales and in Selling, General and Administrative Expenses)

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of employee benefits [text block]

Labor costs (included in Cost of sales and in Selling, general and administrative expenses)

	Year ended December 31,
(all amounts in thousands of U.S. dollars)	2017			2016			2015

Wages, salaries and social security costs		1,144,341			988,794			1,327,968
Severance indemnities		34,497			73,741			176,950
Defined contribution plans		12,401			10,758			13,286
Pension benefits - defined benefit plans		15,066			10,563			14,813
Employee retention and long term incentive program		15,441			16,474			(5,660	)
		1,221,746			1,100,330			1,527,357
From discontinued operations		(853	)		(28,306	)		(24,665	)
		1,220,893			1,072,024			1,502,692

At year-end, the number of employees was

21,605

2017,

19,399

2016

and

21,741

2015.

The following table shows the geographical distribution of the employees:

Country	2017		2016			2015
Argentina		5,221		4,755			5,388
Mexico		5,139		4,968			5,101
Brazil		1,382		1,166			2,050
USA		1,953		1,636			2,190
Italy		2,088		1,979			2,030
Romania		1,870		1,631			1,624
Canada		919		473			546
Indonesia		506		509			532
Colombia		1,003		750			636
Japan		410		458			508
Other		1,114		1,074			1,136
		21,605		19,399			21,741
From discontinued operations		-		(323	)		(292	)
		21,605		19,076			21,449

Note 5 - Other Operating Income and Expenses

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of other operating income (expense) [text block]

Other operating income and expenses

	Year ended December 31,
(all amounts in thousands of U.S. dollars)	2017			2016			2015

Other operating income
Net income from other sales		4,395			16,275			7,480
Net rents		4,325			4,852			6,462
Other		1,796			-			661
		10,516			21,127			14,603

Other operating expenses
Contributions to welfare projects and non-profits organizations		9,158			9,534			9,052
Provisions for legal claims and contingencies		-			10			1
Loss on fixed assets and material supplies disposed / scrapped		118			57			94
Impairment charge		-			-			400,314
Allowance for doubtful receivables		84			432			1,114
Other		-			1,378			-
		9,360			11,411			410,575
From discontinued operations		(1	)		(248	)		(1	)
		9,359			11,163			410,574

Impairment charge

Tenaris regularly conducts assessments of the carrying values of its assets. The value-in-use was used to determine the recoverable value. Value-in-use is calculated by discounting the estimated cash flows over a

five

-year period based on forecasts approved by management. For the subsequent years beyond the

five

-year period, a terminal value is calculated based on perpetuity considering a nominal growth rate of

2%.

Tenaris’s main source of revenue is the sale of products and services to the oil and gas industry and the level of such sales is sensitive to international oil and gas prices and their impact on drilling activities.

For purposes of assessing key assumptions, Tenaris uses external sources of information and management judgment based on past experience.

The main key assumptions used in estimating the value in use are discount rate, growth rate and competitive and economic factors applied to determine Tenaris’s cash flow projections, such as oil and gas prices, average number of active oil and gas drilling rigs (rig count), capital expenditure programs for Tenaris’s customers, and raw material costs.

Management has determined the value of each of the key assumptions as follows:

- Discount rate: based on the applicable weighted average cost of capital (WACC), which is considered to be a good indicator of capital cost, taking into account the industry, country and size of the business. For each CGU where assets are allocated, a specific WACC was determined taking into account the industry, country and size of the business. In

2017,

the main discount rates used were in a range between

9.4%

and

11.2%.

- Growth rate: considers the long-term average growth rate for the oil and gas industry, the higher demand to offset depletion of existing fields and the Company’s expected market penetration.

- Oil and gas prices and customer’s capital expenditures: based on industry analysts’ reports and management’s expectations of market development respectively.

- Rig count: based on information published by Baker Hughes and management’s expectations.

- Raw material costs: based on industry analysts’ reports and management’s expectations.

The main factors that could result in additional impairment charges in future periods would be an increase in the discount rate or a decrease in growth rate used in the Company’s cash flow projections, a further deterioration of the business, competitive and economic factors, such as a decrease in oil and gas prices and the evolution of the rig count.

As of

December 31, 2017,

for those CGUs carrying goodwill, a reasonably possible change in key assumptions would

not

cause the carrying amount to exceed recoverable amount.

2015,

as a result of the deterioration of business conditions, the Company recorded impairment charges on its welded pipe assets of

$400.3

million.

impairment charge was recorded in

2016

2017.

Note 6 - Financial Results

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of finance income (cost) [text block]

Financial results

(all amounts in thousands of U.S. dollars)	Year ended December 31,
	2017			2016			2015

Interest Income		51,525			60,405			39,516
Net result on changes in FV of financial assets at FVTPL		(3,920	)		5,799			(4,942	)
Finance income		47,605			66,204			34,574
Finance cost		(27,072	)		(22,329	)		(23,058	)
Net foreign exchange transactions results (*)		(48,955	)		(2,146	)		(13,301	)
Foreign exchange derivatives contracts results (**)		(8,996	)		(31,310	)		30,468
Other		14,392			11,447			(14,473	)
Other financial results		(43,559	)		(22,009	)		2,694
Net financial results		(23,026	)		21,866			14,210
From discontinued operations		9			88			382
		(23,017	)		21,954			14,592

During

2015

Tenaris has derecognized all its fixed income financial instruments categorized as available for sale.

(*)In

2017

and

2016

includes the negative impact from Euro appreciation against the U.S. dollar on Euro denominated intercompany liabilities in subsidiaries with functional currency U.S. Dollar, largely offset by an increase in currency translation adjustment reserve from an Italian subsidiary.

(**) In

2016

includes the negative impact from Brazilian Real appreciation against the U.S. dollar on hedging instruments and of Cash and cash equivalent and Other investments denominated in U.S. dollar in subsidiaries which functional currency is the Brazilian real, partially offset by an increase in currency translation adjustment reserve from the Brazilian subsidiaries.

Note 7 - Equity in Earnings (Losses) of Non-consolidated Companies

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of investments accounted for using equity method [text block]

Equity in earnings (losses) of non-consolidated companies

	Year ended December 31,
(all amounts in thousands of U.S. dollars)	2017		2016		2015

From non-consolidated companies		116,140		71,533		(10,674	)
Impairment loss on non-consolidated companies (see Note 12)		-		-		(28,884	)
		116,140		71,533		(39,558	)

Note 8 - Income Tax

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of income tax [text block]

Income tax

	Year ended December 31,
(all amounts in thousands of U.S. dollars)	2017			2016			2015

Current tax		184,016			174,410			164,562
Deferred tax		(100,432	)		(132,969	)		79,943
		83,584			41,441			244,505
From discontinued operations		(100,720	)		(24,339	)		(10,121	)
		(17,136	)		17,102			234,384

The tax on Tenaris’s income before tax differs from the theoretical amount that would arise using the tax rate in each country as follows:

	Year ended December 31,
(all amounts in thousands of U.S. dollars)	2017			2016			2015

Income before income tax		427,711			34,430			140,829

Tax calculated at the tax rate in each country (*)		6,456			(91,628	)		(71,588	)
Non taxable income / Non deductible expenses, net (*)		40,298			51,062			149,632
Changes in the tax rates		(62,968	)		4,720			6,436
Effect of currency translation on tax base (**)		(922	)		105,758			151,615
Accrual / Utilization of previously unrecognized tax losses (***)		-			(52,810	)		(1,711	)
Tax charge		(17,136	)		17,102			234,384

(*)

Include the effect of the impairment charges of approximately

$400.3

million in

2015.

(**)

Tenaris applies the liability method to recognize deferred income tax on temporary differences between the tax basis of assets and their carrying amounts in the financial statements. By application of this method, Tenaris recognizes gains and losses on deferred income tax due to the effect of the change in the value on the tax basis in subsidiaries (mainly Mexico, Argentina and Colombia), which have a functional currency different than their local currency. These gains and losses are required by IFRS even though the revalued / devalued tax basis of the relevant assets will

not

result in any deduction / obligation for tax purposes in future periods.

(***)

It includes a deferred tax income of approximately

$45

million booked in the last quarter of

2016

related to a capital loss. Amount was carried forward in line with US Regulation in force, and offset in

2017

Capital Gains.

Changes in the tax rates:

December 29, 2017

Argentina enacted amendments to several tax laws, including among others a reduction in the corporate income tax rate from

35%

30%

for fiscal years starting

January 2018

December 2019

and to

25%

going forward. The impact booked in the Company income tax charge of the year was a gain of approximately

$46

million of deferred tax income.

December 22, 2017

the U.S. enacted significant changes to U.S. tax law. The reform is complex and considers significant changes to the U.S. corporate income tax system by, among others, reducing the Federal corporate income tax rate from

35%

21%.

The Company has made a reasonable estimate of the financial impacts of the reform. However, given its significant changes and complexities, and considering that more accurate information on the impact and the modalities of its application will be obtained in subsequent reporting periods, certain measurement adjustments could be needed.

The impact booked in the Company income tax charge of the year was a gain of approximately

$15.2

million of deferred tax income.

Tax charge

of the year has been affected by an extraordinary charge related to the settlement agreement with the Italian tax authorities (see Note

Note 9 - Dividends Distribution

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of dividends [text block]

Dividends distribution

November 1, 2017,

the Company’s Board of Directors approved the payment of an interim dividend of

$0.13

per share (

$0.26

per ADS), or approximately

$153

million, paid on

November 22, 2017,

with an ex-dividend date of

November 20, 2017.

May 3, 2017,

the Company’s Shareholders approved an annual dividend in the amount of

$0.41

per share (

$0.82

per ADS). The amount approved included the interim dividend previously paid in

November 23, 2016

in the amount of

$0.13

per share (

$0.26

per ADS). The balance, amounting to

$0.28

per share (

$0.56

per ADS), was paid on

May 24, 2017.

In the aggregate, the interim dividend paid in

November 2016

and the balance paid in

May 2017

amounted to approximately

$484.0

million

May 4, 2016

the Company’s Shareholders approved an annual dividend in the amount of

$0.45

per share (

$0.90

per ADS). The amount approved included the interim dividend previously paid in

November 25, 2015

in the amount of

$0.15

per share (

$0.30

per ADS). The balance, amounting to

$0.30

per share (

$0.60

per ADS), was paid on

May 25, 2016.

In the aggregate, the interim dividend paid in

November 2015

and the balance paid in

May 2016

amounted to approximately

$531.2

million.

May 6, 2015

the Company’s Shareholders approved an annual dividend in the amount of

$0.45

per share (

$0.90

per ADS). The amount approved included the interim dividend previously paid in

November 27, 2014

in the amount of

$0.15

per share (

$0.30

per ADS). The balance, amounting to

$0.30

per share (

$0.60

per ADS), was paid on

May 20, 2015.

In the aggregate, the interim dividend paid in

November 2014

and the balance paid in

May 2015

amounted to approximately

$531.2

million.

Note 10 - Property, Plant and Equipment, Net

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of property, plant and equipment [text block]

Property, plant and equipment, net

Year ended December 31, 2017	Land and civil buildings			Industrial buildings, plant and production equipment			Vehicles, furniture and fixtures			Work in progress			Spare parts and equipment			Total

Cost
Values at the beginning of the year		599,710			10,034,500			346,486			1,492,572			25,404			12,498,672
Translation differences		5,493			178,598			5,518			284			331			190,224
Additions		63			7,423			1,252			497,423			18,490			524,651
Disposals / Consumptions		(1,293	)		(3,966	)		(7,319	)		(94	)		(1,812	)		(14,484	)
Increase due to business combinations (*)		2,187			5,654			2,444			-			-			10,285
Transfers / Reclassifications		105,901			1,732,376			22,161			(1,823,106	)		-			37,332
Values at the end of the year		712,061			11,954,585			370,542			167,079			42,413			13,246,680

Depreciation
Accumulated at the beginning of the year		89,274			6,125,552			281,907			-			-			6,496,733
Translation differences		1,204			114,675			4,959			-			-			120,838
Depreciation charge		9,406			368,850			23,213			-			-			401,469
Transfers / Reclassifications		1,699			7,575			(405	)		-			-			8,869
Disposals / Consumptions		(386	)		(3,781	)		(6,205	)		-			-			(10,372	)
Accumulated at the end of the year		101,197			6,612,871			303,469			-			-			7,017,537
At December 31, 2017		610,864			5,341,714			67,073			167,079			42,413			6,229,143

Year ended December 31, 2016	Land and civil buildings			Industrial buildings, plant and production equipment			Vehicles, furniture and fixtures			Work in progress			Spare parts and equipment			Total

Cost
Values at the beginning of the year		609,190			9,683,181			340,835			1,219,369			18,330			11,870,905
Translation differences		2,601			6,737			2,445			2,644			53			14,480
Additions		639			1,384			784			750,038			4,650			757,495
Disposals / Consumptions		(2,296	)		(26,073	)		(10,751	)		(4,850	)		(2,494	)		(46,464	)
Transfer to assets held for sale		(34,849	)		(61,380	)		(1,103	)		(1,407	)		(177	)		(98,916	)
Transfers / Reclassifications		24,425			430,651			14,276			(473,222	)		5,042			1,172
Values at the end of the year		599,710			10,034,500			346,486			1,492,572			25,404			12,498,672

Depreciation
Accumulated at the beginning of the year		88,270			5,844,657			265,487			-			231			6,198,645
Translation differences		508			(3,318	)		1,831			-			(20	)		(999	)
Depreciation charge		9,621			359,516			24,260			-			533			393,930
Transfers / Reclassifications		(160	)		(3,328	)		-			-			(744	)		(4,232	)
Transfer to assets held for sale		(8,552	)		(47,928	)		(966	)		-			-			(57,446	)
Disposals / Consumptions		(413	)		(24,047	)		(8,705	)		-			-			(33,165	)
Accumulated at the end of the year		89,274			6,125,552			281,907			-			-			6,496,733
At December 31, 2016		510,436			3,908,948			64,579			1,492,572			25,404			6,001,939

Property, plant and equipment include capitalized interests for net amounts at

December 31, 2017

and

2016

$39.5

million and

$25.4

million, respectively. The average capitalization interest rates applied were

1.97%

during

2017

and

1.28%

during

2016.

(*) Related to Garrett LLC acquisition, see Note

26.

Note 11 - Intangible Assets, Net

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of intangible assets [text block]

Intangible assets, net

Year ended December 31, 2017	Information system projects			Licenses, patents and trademarks (*)			Goodwill			Customer relationships			Total

Cost
Values at the beginning of the year		554,330			461,619			2,090,257			2,058,946			5,165,152
Translation differences		6,265			483			(184	)		(87	)		6,477
Additions		28,335			5,105			-			-			33,440
Transfers / Reclassifications		(28,371	)		(92	)		-			-			(28,463	)
Increase due to business combinations (**)		133			-			-			-			133
Disposals		-			(1,152	)		-			-			(1,152	)
Values at the end of the year		560,692			465,963			2,090,073			2,058,859			5,175,587

Amortization
Accumulated at the beginning of the year		408,373			362,292			797,592			1,734,068			3,302,325
Translation differences		5,232			-			-			-			5,232
Amortization charge		65,249			10,546			-			131,376			207,171
Transfers / Reclassifications		92			(92	)		-			-			-
Accumulated at the end of the year		478,946			372,746			797,592			1,865,444			3,514,728
At December 31, 2017		81,746			93,217			1,292,481			193,415			1,660,859

Year ended December 31, 2016	Information system projects			Licenses, patents and trademarks (*)			Goodwill			Customer relationships			Total
Cost
Values at the beginning of the year		524,869			494,662			2,170,709			2,059,946			5,250,186
Translation differences		2,264			(29	)		4,671			-			6,906
Additions		28,730			648			-			-			29,378
Transfers / Reclassifications		(546	)		(222	)		-			-			(768	)
Transfer to assets held for sale		(836	)		(32,600	)		(85,123	)		(1,000	)		(119,559	)
Disposals		(151	)		(840	)		-			-			(991	)
Values at the end of the year		554,330			461,619			2,090,257			2,058,946			5,165,152

Amortization
Accumulated at the beginning of the year		335,532			364,412			836,939			1,569,851			3,106,734
Translation differences		1,325			-			-			-			1,325
Amortization charge		72,632			30,633			-			165,217			268,482
Transfers / Reclassifications		(245	)		(153	)		-			-			(398	)
Transfer to assets held for sale		(718	)		(32,600	)		(39,347	)		(1,000	)		(73,665	)
Disposals		(153	)		-			-			-			(153	)
Accumulated at the end of the year		408,373			362,292			797,592			1,734,068			3,302,325
At December 31, 2016		145,957			99,327			1,292,665			324,878			1,862,827

(*) Includes Proprietary Technology.

(**) Related to Garrett LLC acquisition.

The geographical allocation of goodwill for the year ended

December 31, 2017

was

$1,168.5

million for North America,

$121.2

million for South America,

$2.0

million for Europe and

$0.7

million for Middle East & Africa.

The carrying amount of goodwill allocated by CGU, as of

December 31, 2017,

was as follows:

(All amounts in million US dollar)
As of December 31, 2017	Tubes Segment						Other Segment
CGU	Maverick Acquisition		Hydril Acquisition		Other		Maverick Acquisition		Total
OCTG (USA)		225		-		-		-		225
Tamsa (Hydril and other)		-		346		19		-		365
Siderca (Hydril and other)		-		265		93		-		358
Hydril		-		309		-		-		309
Coiled Tubing		-		-		-		4		4
Confab		-		-		28		-		28
Other		-		-		3		-		3
Total		225		920		143		4		1,292

Note 12 - Investments in Non-consolidated Companies

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of interests in other entities [text block]

Investments in non-consolidated companies

	Year ended December 31,
	2017			2016

At the beginning of the year		557,031			490,645
Translation differences		(9,548	)		3,473
Equity in earnings of non-consolidated companies		116,140			71,533
Dividends and distributions received (*)		(22,971	)		(20,674	)
Additions		-			17,108
Decrease / increase in equity reserves and others		(358	)		(5,054	)
At the end of the year		640,294			557,031

(*)Related to Ternium

The principal non-consolidated companies are:

		% ownership at December 31,						Value at December 31,
Company	Country of incorporation	2017			2016			2017		2016
a) Ternium (*)	Luxembourg		11.46	%		11.46	%		563,735		491,285
b) Usiminas (**)	Brazil		3.08	%		3.08	%		70,642		61,904
Others	-		-			-			5,917		3,842
									640,294		557,031

(*) Including treasury shares.

(**)At

December 31, 2017

and

2016

the voting rights were

5.2

a) Ternium S.A.

Ternium S.A. (“Ternium”), is a steel producer with production facilities in Mexico, Argentina, Brazil, Colombia, United States and Guatemala and is

one

of Tenaris’s main suppliers of round steel bars and flat steel products for its pipes business.

December 31, 2017,

the closing price of Ternium’s ADSs as quoted on the New York Stock Exchange was

$31.59

per ADS, giving Tenaris’s ownership stake a market value of approximately

$725.7

million. At

December 31, 2017,

the carrying value of Tenaris’s ownership stake in Ternium, based on Ternium’s IFRS financial statements, was approximately

$563.7

million. See Section

II.B.2.

The Company reviews periodically the recoverability of its investment in Ternium. To determine the recoverable value, the Company estimates the value in use of the investment by calculating the present value of the expected cash flows. The key assumptions used by the Company are based on external and internal sources of information, and on management’s judgment based on past experience and expectations of future changes in the market.

Value-in-use was calculated by discounting the estimated cash flows over a

five

year period based on forecasts approved by management. For the subsequent years beyond the

five

-year period, a terminal value was calculated based on perpetuity. The discount rates used are based on the respective weighted average cost of capital (WACC), which is considered to be a good indicator of capital cost. The discount rate used to test the investment in Ternium for impairment was

11.5%

Summarized selected financial information of Ternium, including the aggregated amounts of assets, liabilities, revenues and profit or loss is as follows:

	Ternium
	2017		2016
Non-current assets		7,727,283		5,622,556
Current assets		4,395,283		2,700,314
Total assets		12,122,566		8,322,870
Non-current liabilities		3,442,521		1,324,785
Current liabilities		2,827,275		1,831,492
Total liabilities		6,269,796		3,156,277

Non-controlling interests		842,347		775,295

Revenues		9,700,296		7,223,975
Gross profit		2,297,271		1,839,585
Net income for the year attributable to owners of the parent		886,219		595,644
Total comprehensive income for the year, net of tax, attributable to owners of the parent		815,434		534,827

b) Usiminas S.A.

Usiminas is a Brazilian producer of high quality flat steel products used in the energy, automotive and other industries and it is Tenaris’s principal supplier of flat steel in Brazil for its pipes and industrial equipment businesses.

As of

December 31, 2017

the closing price of the Usiminas’ ordinary and preferred shares, as quoted on the BM&FBovespa Stock Exchange, was

BRL10.83

(

$3.27

) and

BRL9.1

(

$2.75

), respectively, giving Tenaris’s ownership stake a market value of approximately

$123.0

million. As of that date, the carrying value of Tenaris’s ownership stake in Usiminas was approximately

$70.6

million.

The Company reviews periodically the recoverability of its investment in Usiminas. To determine the recoverable value, the Company estimates the value in use of the investment by calculating the present value of the expected cash flows or its fair value less costs of disposal.

Usiminas financial restructuring process (that started in

April 2016

with the capital increase) was completed by the end of

August 2017.

The completion of this process together with the increase in the share price since

June 2016

and the improvement in business conditions

may

lead to an increase in the value of the investment in Usiminas in future periods.

During

2015

the Company recorded an impairment charge of

$28.9

million.

Summarized selected financial information of Usiminas, including the aggregated amounts of assets, liabilities, revenues and profit or loss is as follows:

	Usiminas
	2017		2016
Non-current assets		5,661,947		6,085,811
Current assets		2,193,096		1,970,015
Total assets		7,855,043		8,055,826
Non-current liabilities		2,344,042		2,856,883
Current liabilities		920,924		537,646
Total liabilities		3,264,966		3,394,529

Non-controlling interests		425,988		508,083

Revenues		3,367,937		2,442,596
Gross profit		513,712		150,999
Net income (loss) for the year attributable to owners of the parent		99,853		(166,153	)

c) Techgen, S.A. de C.V. (“Techgen”)

Techgen is a Mexican natural gas-fired combined cycle electric power plant in the Pesquería area of the State of Nuevo León, Mexico. The company started producing energy on

December 1, 2016

and is fully operational, power capacity of

900

megawatts. As of

December 31, 2017,

Tenaris held

22%

of Techgen’s share capital, and its affiliates, Ternium and Tecpetrol International S.A. (a wholly-owned subsidiary of San Faustin S.A., the controlling shareholder of both Tenaris and Ternium), held

48%

and

30%

respectively.

Techgen is a party to transportation capacity agreements for a purchasing capacity of

150,000

MMBtu/Gas per day starting on

August 1, 2016

and ending on

July 31, 2036,

and a party to a contract for the purchase of power generation equipment and other services related to the equipment. As of

December 31, 2017,

Tenaris’s exposure under these agreements amounted to

$58.2

million and

$3.9

million respectively.

Tenaris issued a corporate guarantee covering

22%

of the obligations of Techgen under a syndicated loan agreement between Techgen and several banks. The loan agreement amounted to

$720

million and has been used in the construction of the facility. The main covenants under the corporate guarantee are Tenaris’s commitment to maintain its participation in Techgen or the right to purchase at least

22%

of Techgen’s firm energy, and compliance with a maximum permitted leverage ratio. As of

December 31, 2017,

the loan agreement had been fully disbursed and, as a result, the amount guaranteed by Tenaris was approximately

$158.4

million. During

2017

the shareholders of Techgen made additional investments in Techgen, in form of subordinated loans, which in case of Tenaris amounted to

million. As of

December 31, 2017,

the aggregate outstanding principal amount under these loans was

$93.2

million.

Note 13 - Receivables - Non Current

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of non-current receivables [text block]

Receivables – non current

	Year ended December 31,
	2017			2016
Government entities		641			913
Employee advances and loans		5,891			7,202
Tax credits		29,404			32,769
Receivables from related parties		88,595			91,419
Legal deposits		13,568			13,876
Advances to suppliers and other advances		12,443			19,520
Others		33,428			32,217
		183,970			197,916
Allowances for doubtful accounts (see Note 22 (i))		(641	)		(913	)
		183,329			197,003

Note 14 - Inventories

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of inventories [text block]

Inventories

	Year ended December 31,
	2017			2016
Finished goods		923,316			653,482
Goods in process		619,796			375,822
Raw materials		281,083			160,284
Supplies		486,002			451,777
Goods in transit		274,175			162,766
		2,584,372			1,804,131
Allowance for obsolescence (see Note 23 (i))		(216,068	)		(240,242	)
		2,368,304			1,563,889

Note 15 - Receivables and Prepayments

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of receivables and prepayments [text block]

15	Receivables and prepayments

	Year ended December 31,
	2017			2016
Prepaid expenses and other receivables		36,587			28,278
Government entities		2,085			3,052
Employee advances and loans		12,205			10,458
Advances to suppliers and other advances		25,205			16,088
Government tax refunds on exports		17,353			9,350
Receivables from related parties		28,397			24,742
Derivative financial instruments		8,230			2,759
Miscellaneous		20,122			36,320
		150,184			131,047
Allowance for other doubtful accounts (see Note 23 (i))		(6,255	)		(6,332	)
		143,929			124,715

Note 16 - Current Tax Assets and Liabilities

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of tax receivables and payables [text block]

16	Current tax assets and liabilities

	Year ended December 31,
Current tax assets	2017		2016
V.A.T. credits		76,714		61,552
Prepaid taxes		55,620		79,434
		132,334		140,986

	Year ended December 31,
Current tax liabilities	2017		2016
Income tax liabilities		35,210		55,841
V.A.T. liabilities		14,313		11,065
Other taxes		52,882		34,291
		102,405		101,197

Note 17 - Trade Receivables

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of trade and other receivables [text block]

17	Trade receivables

	Year ended December 31,
	2017			2016
Current accounts		1,240,769			1,026,026
Receivables from related parties		51,676			14,383
		1,292,445			1,040,409
Allowance for doubtful accounts (see Note 23 (i))		(78,385	)		(85,724	)
		1,214,060			954,685

The following table sets forth details of the aging of trade receivables:

							Past due
	Trade Receivables			Not Due			1 - 180 days			> 180 days
At December 31, 2017
Guaranteed		247,079			219,764			22,978			4,337
Not guaranteed		1,045,366			841,737			115,245			88,384
Guaranteed and not guaranteed		1,292,445			1,061,501			138,223			92,721
Allowance for doubtful accounts		(78,385	)		-			-			(78,385	)
Net Value		1,214,060			1,061,501			138,223			14,336

At December 31, 2016
Guaranteed		355,508			272,393			32,241			50,874
Not guaranteed		684,901			518,984			87,379			78,538
Guaranteed and not guaranteed		1,040,409			791,377			119,620			129,412
Allowance for doubtful accounts		(85,724	)		(62	)		(67	)		(85,595	)
Net Value		954,685			791,315			119,553			43,817

Trade receivables are mainly denominated in

U.S. dollars.

Note 18 - Cash and Cash Equivalents and Other Investments

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of cash and cash equivalents and other investments [text block]

Cash and cash equivalents and Other investments

	Year ended December 31,
	2017		2016
Cash and cash equivalents
Cash at banks		150,948		92,730
Liquidity funds		66,033		215,807
Short – term investments		113,240		91,200
		330,221		399,737
Other investments - current
Fixed Income (time-deposit, zero coupon bonds, commercial papers)		437,406		782,029
Bonds and other fixed Income		754,800		841,638
Fund Investments		-		9,475
Others		100		-
		1,192,306		1,633,142
Other investments - Non-current
Bonds and other fixed Income		123,498		248,049
Others		4,837		1,670
		128,335		249,719

Note 19 - Borrowings

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of borrowings [text block]

Borrowings

	Year ended December 31,
	2017			2016
Non-current
Bank borrowings		34,626			31,544
Finance lease liabilities		59			35
Costs of issue of debt		(40	)		(37	)
		34,645			31,542
Current
Bank borrowings		930,957			807,252
Bank overdrafts		131			1,320
Finance lease liabilities		138			130
Costs of issue of debt		(12	)		(8	)
		931,214			808,694
Total Borrowings		965,859			840,236

The maturity of borrowings is as follows:

	1 year or less		1 - 2 years		2 – 3 years		3 - 4 years		4 - 5 years		Over 5 years		Total
At December 31, 2017
Financial lease		138		59		-		-		-		-		197
Other borrowings		931,076		4,876		4,484		4,978		20,248		-		965,662
Total borrowings		931,214		4,935		4,484		4,978		20,248		-		965,859

Interest to be accrued (*)		14,512		1,212		1,203		1,190		174		-		18,290
Total		945,726		6,147		5,687		6,168		20,422		-		984,149

	1 year or less		1 - 2 years		2 – 3 years		3 - 4 years		4 - 5 years		Over 5 years		Total
At December 31, 2016
Financial lease		130		35		-		-		-		-		165
Other borrowings		808,564		1,198		3,739		3,360		3,632		19,578		840,071
Total borrowings		808,694		1,233		3,739		3,360		3,632		19,578		840,236

Interest to be accrued (*)		6,461		1,172		1,161		1,142		1,116		237		11,289
Total		815,155		2,405		4,900		4,502		4,748		19,815		851,525

(*) Includes the effect of hedge accounting.

Significant borrowings include:

			In million of USD
Disbursement date	Borrower	Type	Original & Outstanding	Final maturity
2017	Tamsa	Bank loans	404	2018
2017	Siderca	Bank loans	311	2018
Dec-17	TuboCaribe	Bank loan	150	Dec-18

As of

December 31, 2017,

Tenaris was in compliance with all of its covenants.

The weighted average interest rates before tax shown below were calculated using the rates set for each instrument in its corresponding currency as of

December 31, 2017

and

2016

(considering hedge accounting where applicable).

		2017				2016
Total borrowings			3.73	%			1.97	%

Breakdown of long-term borrowings by currency and rate is as follows:

Non-current borrowings

		Year ended December 31,
Currency	Interest rates	2017		2016
USD	Fixed		19,120		19,461
EUR	Fixed		13,828		10,701
Others	Variable		1,697		1,380
Total non-current borrowings			34,645		31,542

Breakdown of short-term borrowings by currency and rate is as follows:

Current borrowings

		Year ended December 31,
Currency	Interest rates	2017		2016
USD	Variable		17,640		17,081
USD	Fixed		187,872		200,448
EUR	Variable		169		99
EUR	Fixed		839		841
MXN	Fixed		412,719		391,318
ARS	Fixed		311,829		197,637
ARS	Variable		-		1,041
Others	Variable		138		35
Others	Fixed		8		194
Total current borrowings			931,214		808,694

Borrowings evolution

	Year ended December 31, 2017
	Non current			Current
At the beginning of the year		31,542			808,694
Translation differences		1,649			(3,622	)
Proceeds and repayments, net		1,510			105,142
Interests Accrued less payments		(19	)		21,880
Reclassifications		(309	)		309
Other Movements		272			-
Overdrafts variation		-			(1,189	)
At the end of the year		34,645			931,214

Note 20 - Deferred Income Tax

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of deferred taxes [text block]

Deferred income tax

Deferred income taxes are calculated in full on temporary differences under the liability method using the tax rate of each country.

The evolution of deferred tax assets and liabilities during the year are as follows:

Deferred tax liabilities

	Fixed assets		Inventories			Intangible and Other (*)			Total
At the beginning of the year		263,056		36,891			514,713			814,660
Translation differences		2,243		(2	)		21			2,262
Charged directly to other comprehensive income		-		-			(583	)		(583	)
Income statement credit (charge)		207,605		(1,955	)		(186,544	)		19,106
At December 31, 2017		472,904		34,934			327,607			835,445

	Fixed assets			Inventories			Intangible and Other (*)			Total
At the beginning of the year		299,139			42,516			549,557			891,212
Translation differences		(540	)		-			44			(496	)
Charged directly to other comprehensive income		-			-			(40	)		(40	)
Transfer to assets held for sale		(5,724	)		-			-			(5,724	)
Income statement charge		(29,819	)		(5,625	)		(34,848	)		(70,292	)
At December 31, 2016		263,056			36,891			514,713			814,660

(*) Includes the effect of currency translation on tax base (see Note

Deferred tax assets

	Provisions and allowances			Inventories			Tax losses (*)			Other			Total
At the beginning of the year		(33,276	)		(94,176	)		(199,326	)		(81,838	)		(408,616	)
Translation differences		(223	)		(972	)		322			(606	)		(1,479	)
Charged directly to other comprehensive income		-			-			-			(778	)		(778	)
Income statement charge / (credit)		7,024			5,593			(155,940	)		23,189			(120,134	)
At December 31, 2017		(26,475	)		(89,555	)		(354,944	)		(60,033	)		(531,007	)

(*) As of

December 31, 2017,

the net unrecognized deferred tax assets amount to

$98.8

million.

	Provisions and allowances			Inventories			Tax losses			Other			Total
At the beginning of the year		(32,425	)		(107,378	)		(99,394	)		(102,396	)		(341,593	)
Translation differences		(3,123	)		(1,347	)		(2,741	)		14			(7,197	)
Transfer to assets held for sale		-			275			-			753			1,028
Charged directly to other comprehensive income		-			-			-			1,823			1,823
Income statement charge / (credit)		2,272			14,274			(97,191	)		17,968			(62,677	)
At December 31, 2016		(33,276	)		(94,176	)		(199,326	)		(81,838	)		(408,616	)

The recovery analysis of deferred tax assets and deferred tax liabilities is as follows:

	Year ended December 31,
	2017			2016
Deferred tax assets to be recovered after 12 months		(405,416	)		(226,431	)
Deferred tax liabilities to be recovered after 12 months		808,108			761,039

Deferred income tax assets and liabilities are offset when (

) there is a legally enforceable right to set-off current tax assets against current tax liabilities and (

) when the deferred income taxes relate to the same fiscal authority on either the same taxable entity or different taxable entities where there is an intention to settle the balances on a net basis. The following amounts, determined after appropriate set-off, are shown in the Consolidated Statement of Financial Position:

	Year ended December 31,
	2017			2016
Deferred tax assets		(153,532	)		(144,613	)
Deferred tax liabilities		457,970			550,657
		304,438			406,044

The movement in the net deferred income tax liability account is as follows:

	Year ended December 31,
	2017			2016

At the beginning of the year		406,044			549,619
Translation differences		783			(7,693	)
Charged directly to Other Comprehensive Income		(1,361	)		1,783
Income statement credit		(101,028	)		(132,969	)
Transfer to assets held for sale		-			(4,696	)
At the end of the year		304,438			406,044

Note 21 - Other Liabilities

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of other liabilities [text block]

Other liabilities

(i)

Other liabilities – Non-current

	Year ended December 31,
	2017		2016
Post-employment benefits		125,012		125,161
Other-long term benefits		68,244		66,714
Miscellaneous		24,040		21,742
		217,296		213,617

Post-employment benefits

Unfunded

	Year ended December 31,
	2017			2016
Values at the beginning of the year		96,229			107,601
Translation differences		2,893			(2,204	)
Current service cost		7,851			4,625
Interest cost		5,462			6,371
Curtailments and settlements		21			24
Remeasurements (*)		10,907			(4,501	)
Benefits paid from the plan		(22,107	)		(13,921	)
Other		633			(1,766	)
At the end of the year		101,889			96,229

(*) For

2017

a loss of

$0.08

million is attributable to demographic assumptions and a loss of

$10.6

million to financial assumptions. For

2016

a loss of

$0.6

and a gain of

$5.1

million is attributable to demographic and financial assumptions, respectively.

The principal actuarial assumptions used were as follows:

	Year ended December 31,
	2017	2016
Discount rate	1% - 7%	1% - 7%
Rate of compensation increase	0% - 3%	0% - 3%

As of

December 31, 2017,

an increase / (decrease) of

in the discount rate assumption of the main plans would have generated a (decrease) / increase on the defined benefit obligation of

$8.2

million and

$7.2

million respectively, and an increase / (decrease) of

in the rate of compensation assumption of the main plans would have generated an increase / (decrease) impact on the defined benefit obligation of

$4.0

million and

$4.2

million respectively. The above sensitivity analyses are based on a change in discount rate and rate of compensation while holding all other assumptions constant. In practice, this is unlikely to occur, and changes in some of the assumptions

may

be correlated.

Funded

The amounts recognized in the statement of financial position for the current annual period and the previous annual period are as follows:

	Year ended December 31,
	2017			2016
Present value of funded obligations		165,486			159,612
Fair value of plan assets		(145,692	)		(132,913	)
Liability (*)		19,794			26,699

(*) In

2017

and

2016,

$3.3

million and

$2.2

million corresponding to an overfunded plan were reclassified within other non-current assets, respectively.

The movement in the present value of funded obligations is as follows:

	Year ended December 31,
	2017			2016
At the beginning of the year		159,612			153,974
Translation differences		7,300			384
Current service cost		592			162
Interest cost		6,034			6,403
Remeasurements (*)		3,602			7,753
Benefits paid		(11,654	)		(9,064	)
At the end of the year		165,486			159,612

(*) For

2017

a gain of

$0.4

million is attributable to demographic assumptions and a loss of

$4.1

million to financial assumptions. For

2016

a gain of

$0.9

and a loss of

$8.7

million is attributable to demographic and financial assumptions, respectively.

The movement in the fair value of plan assets is as follows:

	Year ended December 31,
	2017			2016
At the beginning of the year		(132,913	)		(128,321	)
Translation differences		(6,802	)		365
Return on plan assets		(5,849	)		(7,022	)
Remeasurements		(5,874	)		(3,022	)
Contributions paid to the plan		(6,230	)		(4,374	)
Benefits paid from the plan		11,654			9,064
Other		323			397
At the end of the year		(145,692	)		(132,913	)

The major categories of plan assets as a percentage of total plan assets are as follows:

	Year ended December 31,
	2017			2016
Equity instruments		53.4	%		52.4	%
Debt instruments		42.9	%		43.9	%
Others		3.7	%		3.7	%

The principal actuarial assumptions used were as follows:

	Year ended December 31,
	2017			2016
Discount rate		4	%		4	%
Rate of compensation increase		0 % - 3 %			0 % - 3 %

The expected return on plan assets is determined by considering the expected returns available on the assets underlying the current investment policy. Expected return on plan assets is determined based on long-term, prospective rates of return as of the end of the reporting period.

As of

December 31, 2017,

an increase / (decrease) of

in the discount rate assumption of the main plans would have generated a (decrease) / increase on the defined benefit obligation of

$17.0

million and

$20.9

million respectively, and an increase / (decrease) of

in the compensation rate assumption of the main plans would have generated an increase / (decrease) on the defined benefit obligation of

$2.2

million and

$1.8

may

be correlated.

The employer contributions expected to be paid for the year

2018

amount approximately to

$3.5

million.

The methods and types of assumptions used in preparing the sensitivity analysis did

not

change compared to the previous period.

(ii)

Other liabilities – current

	Year ended December 31,
	2017		2016
Payroll and social security payable		141,886		125,991
Liabilities with related parties		51		135
Derivative financial instruments		39,799		42,635
Miscellaneous		15,768		15,126
		197,504		183,887

Note 22 - Non-current Allowances and Provisions

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of non-current allowances and provisions [text block]

Non-current allowances and provisions

Deducted from non-current receivables

	Year ended December 31,
	2017			2016

Values at the beginning of the year		(913	)		(1,112	)
Translation differences		106			199
Used		166			-
Values at the end of the year		(641	)		(913	)

Liabilities

	Year ended December 31,
	2017			2016
Values at the beginning of the year		63,257			61,421
Translation differences		366			3,296
Additional provisions		3,994			6,794
Reclassifications		(7,591	)		(1,932	)
Used		(23,588	)		(6,322	)
Values at the end of the year		36,438			63,257

Note 23 - Current Allowances and Provisions

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of current allowances and provisions [text block]

Current allowances and provisions

(i)

Deducted from assets

Year ended December 31, 2017	Allowance for doubtful accounts - Trade receivables			Allowance for other doubtful accounts - Other receivables			Allowance for inventory obsolescence

Values at the beginning of the year		(85,724	)		(6,332	)		(240,242	)
Translation differences		(345	)		(220	)		(3,575	)
Reversals / (additional) allowances		5,421			(84	)		12,917
Used		2,263			381			14,832
At December 31, 2017		(78,385	)		(6,255	)		(216,068	)

Year ended December 31, 2016	Allowance for doubtful accounts - Trade receivables			Allowance for other doubtful accounts - Other receivables			Allowance for inventory obsolescence

Values at the beginning of the year		(101,480	)		(7,082	)		(229,200	)
Translation differences		(841	)		75			(2,715	)
Reversals / (additional) allowances		12,573			(432	)		(32,765	)
Transfer to held for sale		20			-			896
Used		4,004			1,107			23,542
At December 31, 2016		(85,724	)		(6,332	)		(240,242	)

(ii)

Liabilities

Year ended December 31, 2017	Sales risks			Other claims and contingencies			Total

Values at the beginning of the year		13,885			8,871			22,756
Translation differences		247			227			474
Additional provisions		4,238			9,432			13,670
Reclassifications		-			7,591			7,591
Used		(6,974	)		(5,187	)		(12,161	)
At December 31, 2017		11,396			20,934			32,330

Year ended December 31, 2016	Sales risks			Other claims and contingencies			Total

Values at the beginning of the year		6,290			2,705			8,995
Translation differences		189			(86	)		103
Additional provisions		16,266			7,791			24,057
Reclassifications		(22	)		1,954			1,932
Used		(8,838	)		(3,493	)		(12,331	)
At December 31, 2016		13,885			8,871			22,756

Note 24 - Derivative Financial Instruments

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of derivative financial instruments [text block]

Derivative financial instruments

Net fair values of derivative financial instruments

The net fair values of derivative financial instruments disclosed within Other Receivables and Other Liabilities at the reporting date, in accordance with IAS

39,

are:

	Year ended December 31,
	2017			2016
Foreign exchange derivatives contracts		8,230			2,759
Contracts with positive fair values		8,230			2,759

Foreign exchange derivatives contracts		(39,799	)		(42,635	)
Contracts with negative fair values		(39,799	)		(42,635	)
Total		(31,569	)		(39,876	)

Foreign exchange derivative contracts and hedge accounting

Tenaris applies hedge accounting to certain cash flow hedges of highly probable forecast transactions. The net fair values of exchange rate derivatives and those derivatives that were designated for hedge accounting as of

December 2017

and

2016,

were as follows:

				Fair Value						Hedge Accounting Reserve
Purchase currency	Sell currency	Term		2017			2016			2017			2016
MXN	USD		2018		(20,447	)		(35,165	)		(534	)		9
USD	MXN		2018		490			694			-			(2,280	)
EUR	USD		2018		5,660			(360	)		1,881			-
USD	EUR		2018		(367	)		(33	)		-			(1,435	)
JPY	USD		2018		(101	)		(179	)		-			73
USD	KWD		2018		(630	)		(2,447	)		(520	)		(1,016	)
USD	ARS		2018		22			(748	)		-			-
ARS	USD		2018		(13,715	)		318			(1,067	)		(93	)
USD	BRL		2018		(17	)		(1,581	)		-			-
USD	CAD		2018		(2,072	)		(225	)		-			-
Others					(392	)		(150	)		-			-
Total					(31,569	)		(39,876	)		(240	)		(4,742	)

Following is a summary of the hedge reserve evolution:

	Equity Reserve Dec-15		Movements 2016			Equity Reserve Dec-16			Movements 2017		Equity Reserve Dec-17
Foreign Exchange		2,783		(7,525	)		(4,742	)		4,502		(240	)
Total Cash flow Hedge		2,783		(7,525	)		(4,742	)		4,502		(240	)

Tenaris estimates that the cash flow hedge reserve at

December 31, 2017

will be recycled to the Consolidated Income Statement during

2018.

Note 25 - Contingencies, Commitments and Restrictions On the Distribution of Profits

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of commitments and contingent liabilities [text block]

Contingencies, commitments and restrictions on the distribution of profits

(i)

Contingencies

Tenaris is from time to time subject to various claims, lawsuits and other legal proceedings, including customer claims, in which

third

parties are seeking payment for alleged damages, reimbursement for losses, or indemnity. Management with the assistance of legal counsel periodically reviews the status of each significant matter and assesses potential financial exposure.

Some of these claims, lawsuits and other legal proceedings involve highly complex issues, and often these issues are subject to substantial uncertainties and, therefore, the probability of loss and an estimation of damages are difficult to ascertain. Accordingly, with respect to a large portion of such claims, lawsuits and other legal proceedings, Tenaris is unable to make a reliable estimate of the expected financial effect that will result from ultimate resolution of the proceeding. In those cases, Tenaris has

not

accrued a provision for the potential outcome of these cases.

If a potential loss from a claim, lawsuit or other proceeding is considered probable and the amount can be reasonably estimated, a provision is recorded. Accruals for loss contingencies reflect a reasonable estimate of the losses to be incurred based on information available to management as of the date of preparation of the financial statements, and take into consideration litigation and settlement strategies. In a limited number of ongoing cases, Tenaris was able to make a reliable estimate of the expected loss or range of probable loss and has accrued a provision for such loss, but believes that publication of this information on a case-by-case basis would seriously prejudice Tenaris’s position in the ongoing legal proceedings or in any related settlement discussions. Accordingly, in these cases, the Company has disclosed information with respect to the nature of the contingency, but has

not

disclosed its estimate of the range of potential loss.

The Company believes that the aggregate provisions recorded for potential losses in these consolidated financial statements (Notes

and

) are adequate based upon currently available information. However, if management’s estimates prove incorrect, current reserves could be inadequate and Tenaris could incur a charge to earnings which could have a material adverse effect on Tenaris’s results of operations, financial condition, net worth and cash flows.

Below is a summary description of Tenaris’s material legal proceedings for the year ended

December 31, 2017.

In addition, Tenaris is subject to other legal proceedings,

none

of which is believed to be material.

Tax assessment in Italy

Dalmine S.p.A. (“Dalmine”), an Italian subsidiary of the Company, received on

December 24, 2012,

a tax assessment from the Italian tax authorities related to allegedly omitted withholding tax on dividend payments made in

2007.

The assessment, which was for an estimated amount of

EUR298

million (approximately

$357

million), comprising principal, interest and penalties, was appealed with the

first

-instance tax court in Milan. In

February 2014,

the

first

-instance tax court issued its decision on this tax assessment, partially reversing the assessment and lowering the claimed amount to approximately

EUR9

million (approximately

$11

million), including principal, interest and penalties. On

October 2, 2014,

the Italian tax authorities appealed against the

second

-instance tax court decision on the

2007

assessment. On

June 12, 2015,

the

second

-instance tax court accepted Dalmine’s defense arguments and rejected the appeal by the Italian tax authorities, thus reversing the entire

2007

assessment and recognizing that the dividend payment was exempt from withholding tax. The Italian tax authorities have appealed the

second

-instance tax court decision before the Supreme Court.

December 24, 2013,

Dalmine received a

second

tax assessment from the Italian tax authorities, based on the same arguments as those in the

first

assessment, relating to allegedly omitted withholding tax on dividend payments made in

2008

– the last such distribution made by Dalmine. Dalmine appealed the assessment with the

first

-instance tax court in Milan. On

January 27, 2016,

the

first

-instance tax court rejected Dalmine’s appeal. This

first

-instance ruling, which held that Dalmine is required to pay an amount of

EUR226

million (approximately

$271

million), including principal, interest and penalties, contradicts the

first

and

second

-instance tax court rulings in connection with the

2007

assessment. Dalmine obtained the suspension of the interim payment that would have been due, based on the

first

-instance decision, through the filing with the tax authorities of a bank guarantee of

EUR175

million (approximately

$210

million), and appealed the

January 2016

ruling with the

second

-instance tax court.

December 21, 2017,

Dalmine and the Italian tax authorities entered into a settlement agreement in connection with all withholding tax claims on

2007

and

2008

dividend payments. Under the settlement agreement, Dalmine paid to the Italian tax administration an aggregate amount of

EUR42.9

million (approximately

$51

million), net of

EUR3.2

million (approximately

million) corresponding to the amount previously paid during the litigation proceeding. As a result of the settlement, during the year Tenaris recorded an additional charge to results, in excess of amounts already provisioned, of approximately

$29

million.

In addition, the Italian tax authorities formally notified Dalmine that, based on applicable laws and regulations, any future distributions from Dalmine out of past or future profits will

not

be subject to Italian withholding tax.

CSN claims relating to the

January 2012

acquisition of Usiminas shares

2013,

Confab Industrial S.A. (“Confab”), a Brazilian subsidiary of the Company was notified of a lawsuit filed in Brazil by Companhia Siderúrgica Nacional (CSN) and various entities affiliated with CSN against Confab and the other entities that acquired a participation in Usiminas’ control group in

January 2012.

The CSN lawsuit alleges that, under applicable Brazilian laws and rules, the acquirers were required to launch a tag-along tender offer to all non-controlling holders of Usiminas’ ordinary shares for a price per share equal to

80%

of the price per share paid in such acquisition, or

BRL28.8,

and seeks an order to compel the acquirers to launch an offer at that price plus interest. If so ordered, the offer would need to be made to

182,609,851

ordinary shares of Usiminas

not

belonging to Usiminas’ control group, and Confab would have a

17.9%

share in that offer.

September 23, 2013,

the

first

instance court dismissed the CSN lawsuit, and on

February 8, 2017,

the court of appeals maintained the understanding of the

first

instance court. On

March 6, 2017,

CSN filed a motion for clarification against the decision of the Court of Appeals of São Paulo, which was rejected on

July 19, 2017.

August 18, 2017,

CSN filed an appeal to the Superior Court of Justice seeking the review and reversal of the decision issued by the Court of Appeals. The Superior Court of Justice is restricted to the analysis of alleged violations to federal laws and cannot assess matters of fact. Accordingly, the Court of Appeals must decide whether CSN’s appeal meets the requirements for submission to the Superior Court of Justice. If declared admissible, the Superior Court of Justice will also review admissibility, and, if also declared admissible, will then render a decision on the merits.

Tenaris continues to believe that all of CSN’s claims and allegations are groundless and without merit, as confirmed by several opinions of Brazilian legal counsel,

two

decisions issued by the Brazilian securities regulator (CVM) in

February 2012

and

December 2016,

and the

first

and

second

instance court decisions referred to above. Accordingly,

provision was recorded in these Consolidated Financial Statements.

Veracel celulose accident litigation

September 21, 2007,

an accident occurred in the premises of Veracel Celulose S.A. (“Veracel”) in connection with a rupture in

one

of the tanks used in an evaporation system manufactured by Confab. The Veracel accident allegedly resulted in material damages to Veracel. Itaú Seguros S.A. (“Itaú”), Veracel’s insurer at the time of the Veracel accident, initiated a lawsuit against Confab seeking reimbursement of damages paid to Veracel in connection with the Veracel accident. Veracel initiated a

second

lawsuit against Confab seeking reimbursement of the amount paid as insurance deductible with respect to the Veracel accident and other amounts

not

covered by insurance. Itaú and Veracel claim that the Veracel accident was caused by failures and defects attributable to the evaporation system manufactured by Confab. Confab believes that the Veracel accident was caused by the improper handling by Veracel’s personnel of the equipment supplied by Confab in violation of Confab’s instructions. The

two

lawsuits have been consolidated, and are now being considered by the

6th

Civil Court of São Caetano do Sul; however, each lawsuit will be adjudicated through a separate ruling. Both proceedings are currently at evidentiary stage.

March 10, 2016,

a court-appointed expert issued its report on certain technical matters concerning the Veracel accident. Based upon a technical opinion received from a

third

-party expert, in

August 2016,

Confab filed its objections to the expert’s report. In

November 2017,

the court appointed expert filed a

second

report reaffirming its opinion and stating that the opinion of Confab’s appointed expert was incorrect. The parties have a

-day period to file their observations and/or opinions concerning the expert’s

second

report. Approximately

54%

of the amounts claimed by Itaú and Veracel is attributable to alleged lost profits, and the contract between Confab and Veracel expressly provided that Confab would

not

be liable for damages arising from loss profits. As of

December 31, 2017,

the estimated amount of Itaú’s claim was approximately

BRL81.9

million (approximately

$24.8

million), and the estimated amount of Veracel’s claim is approximately

BRL52

million (approximately

$15.7

million), for an aggregate amount

BRL133.9

million (

$40.5

million). The final result of this claim depends largely on the court’s evaluation of technical matters arising from the expert’s opinion and the objections presented by Confab.

Ongoing investigation

The Company has learned that Italian and Swiss authorities are investigating whether certain payments were made from accounts of entities presumably associated with affiliates of the Company to accounts controlled by an individual allegedly related with officers of Petróleo Brasileiro S.A. and whether any such payments were intended to benefit Confab. Any such payments could violate certain applicable laws, including the U.S. Foreign Corrupt Practices Act. The Company had previously reviewed certain of these matters in connection with an investigation by the Brazilian authorities related to “Operation Lava Jato” and the Audit Committee of the Company’s Board of Directors has engaged external counsel in connection with a review of the alleged payments and related matters. In addition, the Company has voluntarily notified the U.S. Securities and Exchange Commission and the U.S. Department of Justice. The Company intends to share the results of this review with the appropriate authorities, and to cooperate with any investigations that

may

be conducted by such authorities. At this time, the Company cannot predict the outcome of these matters or estimate the range of potential loss or extent of risk, if any, to the Company’s business that

may

result from resolution of these matters.

Petroamazonas penalties

January 22, 2016,

Petroamazonas (“PAM”), an Ecuadorian state-owned oil company, imposed penalties to the Company’s Uruguayan subsidiary, Tenaris Global Services S.A. (“TGS”), for its alleged failure to comply with delivery terms under a pipe supply agreement. The penalties amount to approximately $

22.5

million as of the date hereof. Tenaris believes, based on the advice of counsel, that PAM has

legal basis to impose the penalties and that TGS has meritorious defenses against PAM. However, in light of the prevailing political circumstances in Ecuador, the Company cannot predict the outcome of a claim against a state-owned company and it is

not

possible to estimate the amount or range of loss in case of an unfavorable outcome.

Contractor claim for additional costs

Tenaris Bay City Inc. (“Tenaris Bay City”), a U.S. subsidiary of the Company, has received claims from a contractor for alleged additional costs in the construction of a project located in the Bay City area for a total amount in excess of

$77

million. On

June 30, 2017,

the contractor filed a demand for arbitration of these claims. An arbitral panel has been selected and a scheduling order issued. The parties are expected to submit statements of claim in

February

and

March

2018.

Final trial hearing on this matter is scheduled for

February 2019.

At this stage the Company cannot predict the outcome of the claim or the amount or range of loss in case of an unfavorable outcome.

Investigation

concerning

currency exchange declarations.

Siderca S.A.I.C, an Argentine subsidiary of the Company (“Siderca”), and some of its directors, employees, former directors and employees are subject to an administrative criminal proceeding concerning alleged inaccurate information included in

currency exchange declarations related to the trading of foreign currency between

August

and

October 2008

in connection with exports of goods for a total amount of

$268

million. The case is now under consideration of a criminal court. Although theoretically this proceeding

may

give rise to the application of fines in an amount up to

ten

times the value of the involved operations, Tenaris believes that it has meritorious defenses and that it is unlikely that the ultimate resolution of this matter will result in a material obligation.

Claim for differences on gas supply prices

July 7, 2016,

Siderca was notified of a claim initiated by an Argentine state-owned company for an amount of

$25.4

million, allegedly owed as a result in differences in the price paid for gas supplied to Siderca during

three

months in

2013.

Tenaris believes, based on the advice of counsel, that it has meritorious defenses against a substantial part of this claim, although Siderca

may

be required to pay part of the claimed amount.

Tax assessment in Mexico

August 2017,

Tubos de Acero de México S.A (“Tamsa”) and Servicios Generales Tenaris Tamsa S.A (“Segeta”),

two

Mexican subsidiaries of the Company, were informed that the Mexican tax authorities had determined that the tax deductions associated with purchases of scrap made by the companies during

2013,

amounting to

MXN1,800

million (approximately

$91.2

million) in the aggregate, failed to comply with applicable requirements and, accordingly, should be rejected. Tamsa and Segeta filed their respective responses and complaints against the determination, and provided additional information evidencing compliance with applicable requirements for the tax deductions that are being challenged.

final decision has yet been issued on this matter. Based on the opinion of legal counsel, Tenaris believes that it is unlikely that the ultimate resolution of this tax assessment will result in a material obligation.

(ii)

Commitments and other purchase orders

Set forth is a description of Tenaris’s material outstanding purchase commitments:

A Tenaris company entered into a contract with the supplier Voest Alpine Grobblech Gmb to which it committed to purchase carbon steel for a total amount of approximately

$137

million to use for manufacturing pipes related to the Zhor gas field project.

A Tenaris company entered into a contract with Transportadora de Gas del Norte S.A. for the service of natural gas transportation to the facilities of Siderca S.A.I.C., an Argentine subsidiary of Tenaris. As of

December 31, 2017,

the aggregate commitment to take or pay the committed volumes for a

-year term totalled approximately

$77.5

million.

A Tenaris company entered into a contract with Praxair S.A. for the service of oxygen and nitrogen supply. As of

December 31, 2017,

the aggregate commitment to take or pay the committed volumes for a

-year term totalled approximately

$43.9

million.

Several Tenaris companies entered into a contract with Graftech for the supply of graphite electrodes. As of

December 31, 2017,

the aggregate commitment to take or pay the committed volumes totalled approximately

$78.3

million.

A Tenaris company entered into a

-year contract (effective as of

December 1, 2016,

through

December 1, 2041)

with Techgen for the supply of

197

MW (which represents

22%

of Techgen’s capacity). Monthly payments are determined on the basis of capacity charges, operation costs, back-up power charges, and transmission charges. As of the

seventh

contract year (as long as Techgen’s existing or replacing bank facility has been repaid in full), the Tenaris company has the right to suspend or early terminate the contract if the rate payable under the agreement is higher than the rate charged by the

Comisión Federal de Electricidad

(“CFE”) or its successors. The Tenaris company

may

instruct Techgen to sell to any affiliate, to CFE, or to any other

third

party all or any part of unused contracted energy under the agreement and the Tenaris company will benefit from the proceeds of such sale.

(iii)

Restrictions to the distribution of profits and payment of dividends

As of

December 31, 2017,

equity as defined under Luxembourg law and regulations consisted of:

(all amounts in thousands of U.S. dollars)
Share capital			1,180,537
Legal reserve			118,054
Share premium			609,733
Retained earnings including net income for the year ended December 31, 2017			16,956,761
Total equity in accordance with Luxembourg law			18,865,085

At least

of the Company’s net income per year, as calculated in accordance with Luxembourg law and regulations, must be allocated to the creation of a legal reserve equivalent to

10%

of the Company’s share capital. As of

December 31, 2017,

this reserve is fully allocated and additional allocations to the reserve are

not

required under Luxembourg law. Dividends

may

not

be paid out of the legal reserve.

The Company

may

pay dividends to the extent, among other conditions, that it has distributable retained earnings calculated in accordance with Luxembourg law and regulations.

December 31, 2017,

distributable amount under Luxembourg law totals

$17.6

billion, as detailed below:

(all amounts in thousands of U.S. dollars)
Retained earnings at December 31, 2016 under Luxembourg law	17,493,013
Other income and expenses for the year ended December 31, 2017	(52,232	)
Dividends approved	(484,020	)
Retained earnings at December 31, 2017 under Luxembourg law	16,956,761
Share premium	609,733
Distributable amount at December 31, 2017 under Luxembourg law	17,566,494

Note 26 - Acquisition of subsidiaries

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of business combinations [text block]

Acquisition of subsidiaries

September 2017,

Tenaris acquired

100%

of Garrett (a pipe services and trucking business) through the payment of a price of

$10.4

million.

If the acquisition had occurred on

January 1, 2017,

Tenaris’s unaudited pro forma net sales and net income from continuing operations would

not

have changed materially.

Note 27 - Cash Flow Disclosures

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of cash flow statement [text block]

Cash flow disclosures

			Year ended December 31,
(i)		Changes in working capital	2017			2016			2015
		Inventories		(804,415	)		244,720			936,402
		Receivables and prepayments and Current tax assets		(6,662	)		70,874			60,009
		Trade receivables		(259,375	)		146,824			828,265
		Other liabilities		4,226			(79,046	)		(123,904	)
		Customer advances		17,039			(95,112	)		1,171
		Trade payables		193,905			59,939			(327,958	)
				(855,282	)		348,199			1,373,985
	(ii)	Income tax accruals less payments
		Tax accrued		(17,136	)		41,441			244,505
		Taxes paid		(176,853	)		(169,520	)		(335,585	)
				(193,989	)		(128,079	)		(91,080	)
	(iii)	Interest accruals less payments, net
		Interest accrued		(20,534	)		(43,872	)		(11,517	)
		Interest received		50,001			60,163			56,835
		Interest paid		(17,917	)		(18,858	)		(18,696	)
				11,550			(2,567	)		26,622
	(iv)	Cash and cash equivalents
		Cash at banks, liquidity funds and short - term investments		330,221			399,900			286,547
		Bank overdrafts		(131	)		(1,320	)		(349	)
				330,090			398,580			286,198

Note 28 - Net Assets of Disposal Group Classified As Held for Sale

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of non-current assets held for sale and discontinued operations [text block]

Net assets of disposal group classified as held for sale

December 15, 2016,

Tenaris entered into an agreement with Nucor Corporation (NC) pursuant to which it has sold to NC the steel electric conduit business in North America, known as Republic Conduit for an amount of

$328

million (net of transaction costs). The sale was completed on

January 19, 2017,

with effect from

January 20, 2017.

The result of this transaction was an after-tax gain of

$89.7

million, calculated as the net proceeds of the sale less the book value of net assets held for sale, the corresponding tax effect and related expenses.

	Year ended December 31,
	2017		2016
Income from discontinued operations		1,848		41,411
After tax gain on the sale of Conduit		89,694		-
Net Income for discontinued operations		91,542		41,411

Details of Conduit sale

Cash received	331,295
Transaction and other costs	(3,663	)
Carrying amount of net assets sold	(137,814	)
Gain on sale before income tax	189,817
Income tax expense on gain	(100,123	)
Gain on sale after income tax	89,694

The financial performances presented are relative to the

days of

January 2017

and for the years ended

December 31, 2016

and

2015.

Analysis of the result of discontinued operations:

(all amounts in thousands of US dollars, unless otherwise stated)	2017			2016			2015
Net sales		11,899			234,911			197,630
Cost of sales		(7,403	)		(136,587	)		(137,318	)
Gross profit		4,496			98,324			60,312
Selling, general and administrative expenses		(2,041	)		(32,238	)		(30,678	)
Other operating income & expenses		(1	)		(248	)		(1	)
Operating income		2,454			65,838			29,633
Finance Income (expenses), net		(9	)		(88	)		(382	)
Income before income tax		2,445			65,750			29,251
Income tax		(597	)		(24,339	)		(10,121	)
Net income		1,848			41,411			19,130

Earnings per share attributable to discontinued operations:
Weighted average number of ordinary shares (thousands)		1,180,537			1,180,537			1,180,537
Discontinued operations:
Basic and diluted earnings per share (U.S. dollars per share)		0.00			0.04			0.02
Basic and diluted earnings per ADS (U.S. dollars per ADS)		0.00			0.07			0.03

Summarized cash flow information is as follows

	2017			2016			2015
Cash at the beginning		18,820			15,343			13,848
Cash at the end		206			18,820			15,343
(Decrease) Increase in cash		(18,614	)		3,477			1,495

(Used in) provided by operating activities		(3,046	)		24,535			42,701
Provided by (used in) investing activities		32			(1,058	)		(1,206	)
Used in financing activities		(15,600	)		(20,000	)		(40,000	)

These amounts were estimated only for disclosure purposes, as cash flows from discontinued operations were

not

managed separately from other cash flows.

The following table shows the current and non-current assets and liabilities of disposal group as at

December 2016,

and the carrying amounts of assets and liabilities as at the date of sale.

Current and non-current assets and liabilities of disposal group

ASSETS	At January 19, 2017			At December 31, 2016
Non-current assets
Property, plant and equipment, net		41,438			41,470
Intangible assets, net (*)		45,894	87,332		45,894	87,364
Current assets
Inventories, net		29,349			29,819
Receivables and prepayments, net		1,157			451
Trade receivables, net		38,620			33,620
Cash and cash equivalents		206	69,332		163	64,053
Total assets of disposal group classified as held for sale			156,664			151,417
LIABILITIES
Non-current liabilities
Deferred tax liabilities		5,294			4,696
Other liabilities		-	5,294		680	5,376
Current liabilities
Current tax liabilities		65			4,100
Other liabilities		2,913			1,668
Trade payables		10,578	13,556		6,950	12,718
Total liabilities of disposal group classified as held for sale			18,850			18,094

(*) Includes

$45.8

million of goodwill

Note 29 - Related Party Transactions

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of related party [text block]

Related party transactions

As of

December 31, 2017:

San Faustin S.A., a Luxembourg société anonyme (“San Faustin”), owned

713,605,187

shares in the Company, representing

60.45%

of the Company’s capital and voting rights.

San Faustin owned all of its shares in the Company through its wholly-owned subsidiary Techint Holdings S.à r.l., a Luxembourg société à responsabilité limitée (“Techint”), who is the holder of record of the above-mentioned Tenaris shares.

Rocca & Partners Stichting Administratiekantoor Aandelen San Faustin, a Dutch private foundation (Stichting) (“RP STAK”) held voting shares in San Faustin sufficient in number to control San Faustin.

person or group of persons controls RP STAK.

Based on the information most recently available to the Company, Tenaris’s directors and senior management as a group owned

0.08%

of the Company’s outstanding shares.

Transactions and balances disclosed as with “non-consolidated parties” are those with companies over which Tenaris exerts significant influence or joint control in accordance with IFRS, but does

not

have control. All other transactions and balances with related parties which are

not

non-consolidated parties and which are

not

consolidated are disclosed as “Other”. The following transactions were carried out with related parties:

(all amounts in thousands of U.S. dollars)	Year ended December 31,
	2017		2016		2015
(i) Transactions
(a) Sales of goods and services
Sales of goods to non-consolidated parties		32,362		21,174		24,019
Sales of goods to other related parties		94,624		32,613		87,663
Sales of services to non-consolidated parties		11,637		9,542		10,154
Sales of services to other related parties		3,751		2,948		4,010
		142,374		66,277		125,846
(b) Purchases of goods and services
Purchases of goods to non-consolidated parties		234,361		67,048		260,280
Purchases of goods to other related parties		17,711		20,150		35,153
Purchases of services to non-consolidated parties		12,077		11,528		16,153
Purchases of services to other related parties		50,794		53,530		78,805
		314,943		152,256		390,391

(all amounts in thousands of U.S. dollars)	At December 31,
	2017			2016
(ii) Period-end balances
(a) Arising from sales / purchases of goods / services
Receivables from non-consolidated parties		117,853			117,187
Receivables from other related parties		50,815			13,357
Payables to non-consolidated parties		(49,354	)		(21,314	)
Payables to other related parties		(14,475	)		(12,708	)
		104,839			96,522

Directors’ and senior management compensation

During the years ended

December 31, 2017,

2016

and

2015,

the cash compensation of Directors and Senior managers amounted to

$45.8

million,

$38.6

million and

$28.8

million respectively. These amounts include cash benefits paid to certain senior managers in connection with the vesting of pre-existing retirement plans. In addition, Directors and Senior managers received

484,

500

and

540

thousand units for a total amount of

$4.7

million,

$4.8

million and

$5.4

million respectively in connection with the Employee retention and long term incentive program mentioned in Note O

Employee benefits –Other long term benefits

Note 30 - Principal Subsidiaries

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of interests in subsidiaries [text block]

Principal subsidiaries

The following is a list of Tenaris’s principal subsidiaries and its direct and indirect percentage of ownership of each controlled company at

December 31, 2017.

Company	Country of Incorporation	Main activity	Percentage of ownership at December 31, (*)
			2017	2016	2015
ALGOMA TUBES INC.	Canada	Manufacturing of seamless steel pipes	100%	100%	100%
CONFAB INDUSTRIAL S.A. and subsidiaries	Brazil	Manufacturing of welded steel pipes and capital goods	100%	100%	100%
DALMINE S.p.A.	Italy	Manufacturing of seamless steel pipes	100%	100%	99%
HYDRIL COMPANY and subsidiaries (except detailed) (a)	USA	Manufacture and marketing of premium connections	100%	100%	100%
MAVERICK TUBE CORPORATION and subsidiaries	USA	Manufacturing of welded steel pipes	100%	100%	100%
NKKTUBES	Japan	Manufacturing of seamless steel pipes	51%	51%	51%
P.T. SEAMLESS PIPE INDONESIA JAYA	Indonesia	Manufacturing of seamless steel products	89%	77%	77%
PRUDENTIAL STEEL LTD.	Canada	Manufacturing of welded steel pipes	100%	100%	100%
S.C. SILCOTUB S.A.	Romania	Manufacturing of seamless steel pipes	100%	100%	100%
SIAT SOCIEDAD ANONIMA	Argentina	Manufacturing of welded and seamless steel pipes	100%	100%	100%
SIDERCA SOCIEDAD ANONIMA INDUSTRIAL Y COMERCIAL and subsidiaries	Argentina	Manufacturing of seamless steel pipes	100%	100%	100%
TALTA - TRADING E MARKETING SOCIEDADE UNIPESSOAL LDA.	Portugal	Holding Company	100%	100%	100%
TENARIS BAY CITY, INC.	USA	Manufacturing of seamless steel pipes	100%	100%	100%
TENARIS FINANCIAL SERVICES S.A.	Uruguay	Financial company	100%	100%	100%
TENARIS GLOBAL SERVICES (CANADA) INC.	Canada	Marketing of steel products	100%	100%	100%
TENARIS GLOBAL SERVICES (U.S.A.) CORPORATION	USA	Marketing of steel products	100%	100%	100%
TENARIS GLOBAL SERVICES (UK) LTD	United Kingdom	Holding company and marketing of steel products	100%	100%	100%
TENARIS GLOBAL SERVICES S.A. and subsidiaries (except detailed) (b)	Uruguay	Holding company and marketing of steel products	100%	100%	100%
TENARIS INVESTMENTS S.àr.l.	Luxembourg	Holding company	100%	100%	100%
TENARIS INVESTMENTS SWITZERLAND AG and subsidiaries	Switzerland	Holding company	100%	100%	100%
TENARIS CONNECTIONS BV	Netherlands	Development, management and licensing of intellectual property	100%	100%	100%
TENARIS TUBOCARIBE LTDA.	Colombia	Manufacturing of welded and seamless steel pipes	100%	100%	100%
TUBOS DE ACERO DE MEXICO, S.A.	Mexico	Manufacturing of seamless steel pipes	100%	100%	100%

(*) All percentages rounded.

(a) Tenaris Investments S.a.r.l. holds

100%

of Hydril's subsidiaries shares except for Technical Drilling & Production Services Nigeria. Ltd where it holds

for

2017,

2016

and

2015.

(b) Tenaris holds

97,5%

of Tenaris Supply Chain S.A,

60%

of Gepnaris S.A. and

40%

of Tubular Technical Services and Pipe Coaters, and

49%

of Amaja Tubular Services Limited.

Note 31 - Nationalization of Venezuelan Subsidiaries

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of Nationalization of Subsidiaries [text block]

Nationalization of Venezuelan Subsidiaries

May 2009,

within the framework of Decree Law

6058,

Venezuela’s President announced the nationalization of, among other companies, the Company's majority-owned subsidiaries TAVSA - Tubos de Acero de Venezuela S.A. (“Tavsa”) and, Matesi Materiales Siderúrgicos S.A (“Matesi”), and Complejo Siderúrgico de Guayana, C.A (“Comsigua”), in which the Company has a non-controlling interest (collectively, the “Venezuelan Companies”). Tenaris and its wholly-owned subsidiary, Talta - Trading e Marketing Sociedad Unipessoal Lda (“Talta”), initiated arbitration proceedings against Venezuela before the ICSID in Washington D.C. in connection with these nationalizations.

Matesi

January 29, 2016,

the tribunal released its award on the arbitration proceeding concerning the nationalization of Matesi. The award upheld Tenaris’s and Talta’s claim that Venezuela had expropriated their investments in Matesi in violation of Venezuelan law as well as the bilateral investment treaties entered into by Venezuela with the Belgium-Luxembourg Economic Union and Portugal. The award granted compensation in the amount of

$87.3

million for the breaches and ordered Venezuela to pay an additional amount of

$85.5

million in pre-award interest, aggregating to a total award of

$172.8

million, payable in full and net of any applicable Venezuelan tax, duty or charge. The tribunal granted Venezuela a grace period of

six

months from the date of the award to make payment in full of the amount due without incurring post-award interest, and resolved that if

no,

full, payment is made by then, post-award interest will apply at the rate of

per annum. As of

December 31, 2017,

post-award interest amounted to

$31.9

million.

March 14, 2016,

Venezuela requested the rectification of the award pursuant to article

(

) of the ICSID Convention and ICSID Arbitration Rule

49.

The tribunal denied Venezuela’s request on

June 24, 2016,

ordering Venezuela to reimburse Tenaris and Talta for their costs. On

September 21, 2016,

Venezuela submitted a request for annulment of the award as well as the stay of enforcement of the award in accordance with the ICSID Convention and Arbitration Rules, and the ad hoc committee that will hear Venezuela’s request was constituted on

December 27, 2016.

March 24, 2017,

the ad hoc committee rendered its decision to lift the stay of enforcement of the award. The ad hoc committee has

not

reserved its right to reopen that decision and

appeal against such decision is provided under ICSID’s Arbitration Rules.

The parties exchanged

two

rounds of written submissions on Venezuela’s request for annulment. Following the resignation of

one

of the ad hoc committee members, the committee was reconstituted on

November 3, 2017,

and the final hearing on Venezuela’s annulment request was rescheduled for

March 22-

23,

2018.

Following the hearing, the ad hoc committee will deliberate and issue a decision on Venezuela’s annulment application. While there is

deadline by which the ad hoc committee must render its decision, it is presently expected that the ad hoc committee will render a decision between

June

and

September 2018.

Tavsa and Comsigua

December 12, 2016,

the tribunal issued its award upholding Tenaris’s and Talta’s claim that Venezuela had expropriated their investments in Tavsa and Comsigua in violation of the bilateral investment treaties entered into by Venezuela with the Belgium-Luxembourg Economic Union and Portugal. The award granted compensation in the amount of

$137

million and ordered Venezuela to reimburse Tenaris and Talta

$3.3

million in legal fees and ICSID administrative costs. In addition, Venezuela was ordered to pay interest from

April 30, 2008

until the day of effective payment at a rate equivalent to LIBOR +

per annum, which as of

December 31, 2017

amounted to

$88

million.

April 11, 2017,

Venezuela submitted a request for annulment of the award as well as the stay of enforcement of the award in accordance with the ICSID Convention and Arbitration Rules. Venezuela’s annulment request was registered on

April 14, 2017.

The ad hoc committee that will hear Venezuela’s request was constituted on

October 17, 2017.

October 19, 2017,

Tenaris and Talta filed an opposition to Venezuela’s request to continue the stay of enforcement of the award, which was followed by the exchange of additional written submissions between the parties. The ad hoc committee has extended the provisional stay of enforcement of the award until it rules on Venezuela’s request. A hearing on Venezuela’s request to continue the stay of enforcement of the award was held on

February 1, 2018,

and will be followed by a decision from the ad hoc committee. The final hearing for Venezuela’s annulment request is scheduled for

August 27-

28,

2018.

Following the hearing, the ad hoc committee will deliberate and issue a decision on Venezuela’s annulment application. While there is

deadline by which the ad hoc committee must render its decision, it is presently expected that the ad hoc committee will render a decision between

November 2018

and

February 2019.

Based on the facts and circumstances described above and following the guidance set forth by IAS

27R,

the Company ceased consolidating the results of operations and cash flows of the Venezuelan Companies as from

June 30, 2009,

and classified its investments in the Venezuelan Companies as financial assets based on the definitions contained in paragraphs

(c)(i) and

of IAS

32.

The Company classified its interests in the Venezuelan Companies as available-for-sale investments since management believes they do

not

fulfil the requirements for classification within any of the remaining categories provided by IAS

and such classification is the most appropriate accounting treatment applicable to non-voluntary dispositions of assets.

Tenaris or its subsidiaries have net receivables with the Venezuelan Companies as of

December 31, 2017,

for a total amount of approximately

$27

million.

The Company records its interest in the Venezuelan Companies at its carrying amount at

June 30, 2009,

and

not

at fair value, following the guidance set forth by paragraphs

(c),

AG80

and

AG81

of IAS

39.

Note 32 - Fees Paid to the Company's Principal Accountant

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of additional information [text block]

Fees paid to the Company's principal accountant

Total fees accrued for professional services rendered by PwC Network firms to Tenaris S.A. and its subsidiaries are detailed as follows:

(all amounts in thousands of U.S. dollars)	Year ended December 31,
	2017		2016		2015
Audit fees		3,995		3,588		4,372
Audit-related fees		88		64		78
Tax fees		23		14		25
All other fees		30		3		15
Total		4,136		3,669		4,490

Note 33 - Subsequent Event

12 Months Ended

Dec. 31, 2017

Statement Line Items [Line Items]

Disclosure of events after reporting period [text block]

Subsequent event

Agreement regarding governance of Usiminas

February 8, 2018,

the Company’s affiliate Ternium announced that its subsidiary Ternium Investments S.à r.l. had entered into a binding and immediately effective agreement (the “Agreement”) with Nippon Steel & Sumitomo Metal Corporation (“NSSMC”), establishing certain new governance rules for Usiminas as well as certain undertakings for the settlement of legal disputes. The new governance rules for Usiminas include, among others, an alternation mechanism for the nomination of each of the CEO and the Chairman of the Usiminas board of directors, as well as a new mechanism for the nomination of other members of Usiminas’ executive board. In addition, the Agreement incorporates an exit mechanism.

Under the Agreement, the right to nominate the CEO and the Chairman will alternate between Ternium and NSSMC at a

-year interval, comprising

two

consecutive

-year terms. For the initial

four

years, Ternium will be entitled to nominate the CEO and NSSMC will be entitled to nominate the Chairman. Initially, Ternium and NSSMC intend to nominate Sergio Leite as Usiminas’ CEO and Ruy Hirschheimer as Usiminas’ Chairman of the Board, respectively. The executive board will be composed of

six

members, including the CEO and

five

Vice-Presidents, with Ternium and NSSMC nominating

three

members each. The Agreement includes an exit mechanism consisting of a buy-and-sell procedure, exercisable at any time during the term of the existing Usiminas shareholders' agreement after the

fourth

-and-a-half-year anniversary from the coming election of Usiminas’ executive board in

May 2018.

Such buy-and-sell procedure would allow either Ternium or NSSMC to purchase all or a majority of the Usiminas shares held by the other party.

The Company’s subsidiary Confab Industrial, together with Ternium Investments S.à r.l. and its subsidiaries Siderar S.A.I.C. and Prosid Investments, is a party to the T/T Group within the Usiminas controlling group. Pursuant to the Agreement, the T/T Group members, including Confab, will use their reasonable best efforts to negotiate and execute an amended and restated Usiminas’ shareholders’ agreement together with the other minority shareholders of the control group, Previdência Usiminas, Metal One Corporation and Mitsubishi Corporation do Brasil S.A., having the same termination date as the existing Usiminas shareholders’ agreement. If any non-affiliated controlling group shareholder for any reason does

not

enter into the new shareholders agreement on or before

April 10, 2018,

the T/T Group members, including Confab, will enter into a separate Usiminas’ shareholders’ agreement only among themselves and their affiliates that are shareholders of Usiminas, which will operate as an upper-level agreement in respect of the existing shareholders agreement and will more fully reflect and implement the new governance rules as between them and their affiliates.

Annual Dividend Proposal

February 21, 2018

the Company’s Board of Directors proposed, for the approval of the Annual General Shareholders' meeting to be held on

May 2, 2018,

the payment of an annual dividend of

$0.41

per share (

$0.82

per ADS), or approximately

$484

million, which includes the interim dividend of

$0.13

per share (

$0.26

per ADS) or approximately

$153

million, paid on

November 22, 2017.

If the annual dividend is approved by the shareholders, a dividend of

$0.28

per share (

$0.56

per ADS), or approximately

$331

million will be paid on

May 23, 2018,

with an ex-dividend date of

May 21, 2018.

These Consolidated Financial Statements do

not

reflect this dividend payable.

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Discloure of Significant Accounting Policies

Description of accounting policy for basis of presentation [text block]

Basis of presentation

Whenever necessary, certain comparative amounts have been reclassified to conform to changes in presentation in the current year.

28,

as well as additional information detailing net assets of disposal group classified as held for sale and discontinued operations.

may

differ from these estimates.

(

)

New and amended standards

not

yet adopted and relevant for Tenaris

IFRS

“Financial instruments”

July 2014,

the IASB issued IFRS

"Financial instruments", which replaces the guidance in IAS

39.

IFRS

39.

It also introduces new rules for hedge accounting. IFRS

must be applied on annual periods beginning on or after

January 1, 2018.

The Company will apply the new rules retrospectively from

January 2018.

Comparative amounts for previous years will

not

be restated.

million.

million in the allowance for doubtful accounts.

The Company does

not

expect any significant impact related to the new hedge accounting rules.

IFRS

15,

“Revenue from contracts with customers”

May 2014,

the IASB issued IFRS

15,

must be applied on annual periods beginning on or after

January 1, 2018.

The Company has assessed the effects of applying the new standard and the main areas affected will be the accounting for sales of shipping services, free of charge services and rights of return.

The impact of the adoption as of

January 1, 2018

on the aggregate of revenues, cost of sales and selling expenses is expected to be a decrease of $

0.7

million net.

The Company intends to adopt this standard using the modified retrospective approach, meaning that the cumulative impact of the adoption will be recognized in retained earnings as of

January 1, 2018

and that comparatives will

not

be restated.

IFRS

16,

“Leases”

January 2016,

the IASB issued IFRS

16,

"Leases". The new standard will result in almost all leases recognized on the balance sheet, as the distinction between operating and finance leases is removed. IFRS

must be applied on annual periods beginning on or after

January 1, 2019.

The Company's management is currently assessing the potential impact that the application of this standard

may

have on the Company's financial condition or results of operations.

These standards were endorsed by the EU.

Other accounting pronouncements that became effective during

2017

have

material effect on the Company’s financial condition or results of operations.

Description of accounting policy for investment in associates and joint ventures [text block]

Group accounting

(

)

Subsidiaries and transactions with non-controlling interests

longer consolidated from the date control ceases.

Transactions with non-controlling interests that do

not

Other financial results

(

)

Non-consolidated companies

Non-consolidated companies are all entities in which Tenaris has significant influence but

not

control, generally accompanying a shareholding of between

20%

and

50%

The Company’s pro-rata share of earnings in non-consolidated companies is recorded in the Consolidated Income Statement under

Equity in earnings (losses) of non-consolidated companies

. The Company’s pro-rata share of changes in other reserves is recognized in the Consolidated Statement of Changes in Equity under

Other Reserves.

December 31, 2017,

Tenaris holds

11.46%

of Ternium S.A (“Ternium”)’s common stock. The following factors and circumstances evidence that Tenaris has significant influence (as defined by IAS

28,

“Investments in associates companies and Joint Ventures”) over Ternium, and as a result the Company’s investment in Ternium has been accounted for under the equity method:

Both the Company and Ternium are under the indirect common control of San Faustin S.A.;

Four out of

eight

members of Ternium’s Board of Directors (including Ternium’s chairman) are also members of the Company’s Board of Directors;

Under the shareholders’ agreement by and between the Company and Techint Holdings S.à r.l, a wholly owned subsidiary of San Faustin S.A. and Ternium’s main shareholder, dated

January 9, 2006,

Techint Holdings S.à r.l, is required to take actions within its power to cause (a)

one

December 31, 2017,

Tenaris holds through its Brazilian subsidiary Confab Industrial S.A. (“Confab”),

5.2%

of the shares with voting rights and

3.08%

of Usinas Siderúrgicas de Minas Gerais S.A. (“Usiminas”) total share capital.

The acquisition of Usiminas shares was part of a larger transaction performed

January 16, 2012,

pursuant to which Ternium, certain of its subsidiaries and Confab joined Usiminas’ existing control group through the acquisition of ordinary shares representing

27.7%

of Usiminas’ total voting capital and

13.8%

of Usiminas’ total share capital.

The rights of Ternium and its subsidiaries and Confab within the Ternium - Tenaris Group are governed under a separate shareholders agreement.

Those circumstances evidence that Tenaris has significant influence over Usiminas, consequently, accounted it for under the equity method (as defined by IAS

April

and

May 2016

Tenaris’s subsidiary Confab subscribed, in the aggregate, to

1.3

million preferred shares (

BRL1.28

per share) for a total amount of

BRL1.6

million (approximately

$0.5

million) and

11.5

million ordinary shares (

BRL5.00

per share) for a total amount of

BRL57.5

million (approximately

$16.6

million). The preferred and ordinary shares were issued on

June 3, 2016

and

July 19, 2016,

respectively. Consequently as of

December 31, 2017

Tenaris owns

36.5

million ordinary shares and

1.3

million preferred shares of Usiminas.

Tenaris carries its investment in Ternium and Usiminas under the equity method, with

may

not

be recoverable, such as a significant or prolonged decline in fair value below the carrying value. At

December 31, 2017,

2016

and

2015,

impairment provisions were recorded on Tenaris’s investment in Ternium while in

2015,

an impairment charge was recorded on Tenaris’s investment in Usiminas. See Note

and Note

12.

Description of accounting policy for segment reporting [text block]

Segment information

The Company is organized in

one

major business segment, Tubes, which is also the reportable operating segment.

Others includes all other business activities and operating segments that are

not

The use of direct cost methodology to calculate the inventories, while under IFRS it is at full cost, including absorption of production overheads and depreciations;

The use of costs based on previously internally defined cost estimates, while, under IFRS, costs are calculated at historical cost;

Other timing differences, if any.

Tenaris presents its geographical information in

five

Description of accounting policy for foreign currency translation [text block]

Foreign currency translation

(

)

Functional and presentation currency

IAS

(revised) “The effects of changes in foreign exchange rates” defines the functional currency as the currency of the primary economic environment in which an entity operates.

Sales are mainly negotiated, denominated and settled in U.S. dollars. If priced in a currency other than the U.S. dollar, the sales price

may

consider exposure to fluctuation in the exchange rate versus the U.S. dollar;

Prices of their critical raw materials and inputs are priced and settled in U.S. dollars;

Transaction and operational environment and the cash flow of these operations have the U.S. dollar as reference currency;

Significant level of integration of the local operations within Tenaris’s international global distribution network;

Net financial assets and liabilities are mainly received and maintained in U.S. dollars;

The exchange rate of certain legal currencies has long-been affected by recurring and severe economic crises.

(

)

Transactions in currencies other than the functional currency

“Other financial results”

in the Consolidated Income Statement, except when deferred in equity as qualifying cash flow hedges and qualifying net investment hedges.

(

)

Translation of financial information in currencies other than the functional currency

Results of operations for subsidiaries whose functional currencies are

not

Goodwill and fair value adjustments arising from the acquisition of a foreign operation are treated as assets and liabilities of the foreign operation and translated at the closing rate.

Description of accounting policy for property, plant and equipment [text block]

Property, plant and equipment

Cost

may

also include transfers from equity of any gains or losses on qualifying cash flow hedges of foreign currency purchases of property, plant and equipment.

Borrowing costs that are attributable to the acquisition or construction of certain capital assets are capitalized as part of the cost of the asset, in accordance with IAS

(R) “Borrowing Costs”. Assets for which borrowing costs are capitalized are those that require a substantial period of time to prepare for their intended use.

	Land	No Depreciation
	Buildings and improvements	30-50 years
	Plant and production equipment	10-40 years
	Vehicles, furniture and fixtures, and other equipment	4-10 years

Management’s re-estimation of assets useful lives, performed in accordance with IAS

“Property, Plant and Equipment”, did

not

materially affect depreciation expenses for

2017,

2016

and

2015.

During

2017,

Gains and losses on disposals are determined by comparing the proceeds with the carrying amount of assets and are recognized under

Other operating income

Other operating expenses

in the Consolidated Income Statement.

Description of accounting policy for intangible assets and goodwill [text block]

Intangible assets

(

)

Goodwill

not

reversed. Goodwill is included in the Consolidated Statement of Financial Position under

Intangible assets, net.

(

)

Information systems projects

one

year and comply with the recognition criteria of IAS

38.

Information systems projects recognized as assets are amortized using the straight-line method over their useful lives, generally

not

exceeding a period of

years. Amortization charges are mainly classified as

Selling, general and administrative expenses

in the Consolidated Income Statement.

Management’s re-estimation of assets useful lives, performed in accordance with IAS

“Intangible Assets”, did

not

materially affect amortization expenses for

2017,

2016

and

2015.

(

)

Licenses, patents, trademarks and proprietary technology

not

exceed a period of

years. Amortization charges are mainly classified as

Selling, general and administrative expenses

in the Consolidated Income Statement.

The balance of acquired trademarks that have indefinite useful lives according to external appraisal amounts to

86.7

million at

December 31, 2017

and

2016,

Management’s re-estimation of assets useful lives, performed in accordance with IAS

38,

did

not

materially affect amortization expenses for

2017,

2016

and

2015.

(

)

Research and development

Research expenditures as well as development costs that do

not

fulfill the criteria for capitalization are recorded as

Cost of sales

in the Consolidated Income Statement as incurred. Research and development expenditures included in

Cost of sales

for the years

2017,

2016

and

2015

totaled

$63.7

million,

$68.6

million and

$89.0

million, respectively.

(

)

Customer relationships

In accordance with IFRS

"Business Combinations" and IAS

38,

Tenaris has recognized the value of customer relationships separately from goodwill attributable to the acquisition of Maverick and Hydril groups.

years for Maverick and

years for Hydril.

2015

the Company reviewed the useful life of Prudential’s customer relationships, related to Maverick acquisition, and decided to reduce the remaining amortization period from

years to

years, ending

December 2017.

As of

December 2017

the residual value of Maverick’s customer relationships amount to

$193

million and the residual useful life is

years, while Hydril’s customer relationships is fully amortized

Description of accounting policy for impairment of non-financial assets [text block]

Impairment of non-financial assets

Assets that are subject to amortization are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount

may

not

be recoverable. Intangible assets with indefinite useful lives, including goodwill, are subject to at least an annual impairment test.

In assessing whether there is any indication that a CGU

may

(a)

first, to reduce the carrying amount of any goodwill allocated to the CGU; and

(b)

then, to the other assets of the unit (group of units) pro-rata on the basis of the carrying amount of each asset in the unit (group of units), considering

not

to reduce the carrying amount of the asset below the highest of its fair value less cost of disposal, its value in use or zero.

The value in use of each CGU is determined on the basis of the present value of net future cash flows which would be generated by such CGU. Tenaris uses cash flow projections for a

five

year period with a terminal value calculated based on perpetuity and appropriate discount rates.

For purposes of calculating the fair value less costs of disposal, Tenaris uses the estimated value of future cash flows that a market participant could generate from the corresponding CGU.

Non-financial assets other than goodwill that suffered an impairment are reviewed for possible reversal at each reporting date.

Description of accounting policy for investments other than investments accounted for using equity method [text block]

Other investments

Other investments consist primarily of investments in financial instruments and time deposits with a maturity of more than

three

months at the date of purchase.

Financial Results

in the Consolidated Income Statement using the effective interest method. Held to maturity instruments with maturities greater than

months after the balance sheet date are included in the non-current assets.

Financial Results

in the Consolidated Income Statement.

Purchases and sales of financial investments are recognized as of their settlement date.

The fair values of quoted investments are generally based on current bid prices. If the market for a financial investment is

not

active or the securities are

not

listed, Tenaris estimates the fair value by using standard valuation techniques (see Section III Financial Risk Management).

Description of accounting policy for measuring inventories [text block]

Inventories

Description of accounting policy for trade and other receivables [text block]

Trade and other receivables

180

days and which are

not

covered by a credit collateral, guarantee, insurance or similar surety, are provisioned.

Description of accounting policy for determining components of cash and cash equivalents [text block]

Cash and cash equivalents

Cash and cash equivalents are comprised of cash at banks, liquidity funds and short-term investments with a maturity of less than

three

In the Consolidated Statement of Financial Position, bank overdrafts are included in

Borrowings

in current liabilities.

For the purposes of the Consolidated Statement of Cash Flows, cash and cash equivalents includes overdrafts.

Description of accounting policy for issued capital [text block]

Equity

(

)

Equity components

The Consolidated Statement of Changes in Equity includes:

The value of share capital, legal reserve, share premium and other distributable reserves calculated in accordance with Luxembourg law;

The currency translation adjustment, other reserves, retained earnings and non-controlling interest calculated in accordance with IFRS.

(

)

Share capital

The Company has an authorized share capital of a single class of

2.5

billion shares having a nominal value of

$1.00

per share. Total ordinary shares issued and outstanding as of

December 31, 2017,

2016

and

2015

are

1,180,536,830

with a par value of

1.00

per share with

one

vote each. All issued shares are fully paid.

(

)

Dividends distribution by the Company to shareholders

Dividends

may

be paid by the Company to the extent that it has distributable retained earnings, calculated in accordance with Luxembourg law (see Note

(iii)).

Description of accounting policy for borrowings [text block]

Borrowings

Description of accounting policy for current and deferred income tax [text block]

Current and Deferred income tax

Deferred tax liabilities and assets are

not

reverse in the foreseeable future.

Description of accounting policy for employee benefits [text block]

Employee benefits

(

)

Short-term obligations

(

)

Post employment benefits

one

or more factors such as age, years of service and compensation.

Remeasurement gains and losses arising from experience adjustments and changes in actuarial assumptions are charged or credited to equity in

Other comprehensive income

in the period in which they arise. Past-service costs are recognized immediately in the Income Statement.

Tenaris sponsors funded and unfunded defined benefit pension plans in certain subsidiaries. The most significant are:

December 31, 2017

the outstanding liability for this plan amounts to

$46.8

million.

January 1, 2007

further obligation. As a result, the plan changed from a defined benefit plan to a defined contribution plan effective from that date, but only limited to the contributions of

2007

onwards. As of

December 31, 2017

the outstanding liability for this plan amounts to

$19.3

million.

June 2016

the salary plan was frozen for the purposes of credited service as well as determination of final average pay. As of

December 31, 2017

the outstanding liability for this plan amounts to

$16.7

million.

December 31, 2017

the outstanding liability for this plan amounts to

$12.3

million.

(

)

Other long term benefits

During

2007,

four

years and will be mandatorily redeemed by the Company

ten

years after grant date, with the option of an early redemption at

seven

years after the grant date. As the cash payment of the benefit is tied to the book value of the shares, and

not

to their market value, Tenaris valued this long-term incentive program as a long term benefit plan as classified in IAS

“Employee Benefits”.

As of

December 31, 2017

and

2016,

the outstanding liability corresponding to the Program amounts to

$79.2

million and

$78.7

million, respectively. The total value of the units granted (vested and unvested) to date under the program, considering the number of units and the book value per share as of

December 31, 2017

and

2016,

$94.8

million and

$92.9

million, respectively.

(

)

Termination benefits

longer withdraw the offer of those benefits; and (b) when the costs for a restructuring that is within the scope of IAS

(

)

Other compensation obligations

Employee entitlements to annual leave and long-service leave are accrued as earned.

Compensation to employees in the event of dismissal is charged to income in the year in which it becomes payable.

Description of accounting policy for provisions [text block]

Provisions

Tenaris is subject to various claims, lawsuits and other legal proceedings, including customer claims, in which a

third

may

be changes in the estimates of future costs which could have a material adverse effect on its results of operations, financial condition and cash flows.

This note should be read in conjunction with Note

25.

Description of accounting policy for trade and other payables [text block]

Trade and other payables

not

due within

months after the reporting period.

Description of accounting policy for recognition of revenue [text block]

Revenue recognition

may

include delivery to a storage facility located at

one

The percentage of total sales that were generated from bill and hold arrangements for products located in Tenaris’s storage facilities that have

not

been shipped to customers amounted to

3.3%,

2.8%

and

3.0%

as of

December 31, 2017,

2016

and

2015,

respectively. The Company has

not

experienced any material claims requesting the cancellation of bill and hold transactions.

Other revenues earned by Tenaris are recognized on the following basis:

Construction contracts (mainly applicable to Tenaris Brazilian subsidiaries and amounted to

$11

million,

0.21%

of total sales). The revenue recognition of the contracts follows the IAS

Interest income: on the effective yield basis.

Dividend income from investments in other companies: when Tenaris’s right to receive payment is established.

Description of accounting policy for expenses [text block]

Cost of sales and other selling expenses

Cost of sales and other selling expenses are recognized in the Consolidated Income Statement on the accrual basis of accounting.

Commissions, freights and other selling expenses, including shipping and handling costs, are recorded in

Selling, general and administrative expenses

in the Consolidated Income Statement.

Description of accounting policy for earnings per share [text block]

Earnings per share

Earnings per share are calculated by dividing the income attributable to owners of the parent by the daily weighted average number of common shares outstanding during the year.

There are

dilutive potential ordinary shares.

Description of accounting policy for financial instruments [text block]