Income tax

	Year ended December 31,
(all amounts in thousands of U.S. dollars)	2019			2018			2017

Current tax		299,692			343,104			184,016
Deferred tax		(97,240	)		(113,897	)		(100,432	)
		202,452			229,207			83,584
From discontinued operations		-			-			(100,720	)
		202,452			229,207			(17,136	)

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)	2019			2018			2017

Income before income tax		933,710			1,103,107			427,711

Tax calculated at the tax rate in each country		186,752			207,422			6,456
Effect of currency translation on tax base		53,296			77,552			(922	)
Changes in the tax rates		(13	)		1,824			(62,968	)
Utilization of previously unrecognized tax losses		(547	)		-			-
Tax revaluation, withholding tax and others		(37,036	)		(57,591	)		40,298
Tax charge		202,452			229,207			(17,136	)

Effect of currency translation on tax base,

Tenaris applies the liability method to recognize deferred income tax on temporary differences between the tax bases of assets/liabilities 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 Argentina and Mexico), which have a functional currency different than their local currency. These gains and losses are required by IFRS even though the revalued / devalued tax bases of the relevant assets will

not

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

Tax revaluation, withholding tax and others,

mainly includes a net tax income of

$66

and

$65

million for

2019

and

2018

respectively related to the tax revaluation regime in Argentina and Mexico; it also includes a charge of

$34

and

$26

million for

2019

and

2018

respectively related to withholding taxes for intra group international operations.

Changes in the tax rates

, in

2017

it includes mainly the effect of the changes in tax rate in Argentine and US subsidiaries for approximately

$46

million and

$15

million respectively.