Note 12. Income Taxes

We are subject to U.S. federal, state and foreign corporate income taxes. The provision for income taxes is based on income (loss) before provision for income taxes as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
U.S.	$	36,493	$	272,574	$	110,560
Non-U.S.		(348,783)		(165,170)		(103,004)
Income (loss) before income taxes	$	(312,290)	$	107,404	$	7,556

Our provision for income taxes consists of the following (in thousands):


	Year Ended December 31,
	2017		2016		2015
Current:
State	$	486	$	2,700	$	1,025
Foreign		1,171		482		—
		1,657		3,182		1,025
Deferred:
State		(805)		—		—
Foreign		—		—		—
		(805)		—		—
Total provision for income taxes	$	852	$	3,182	$	1,025

A reconciliation of income taxes at the U.S. federal statutory rate to the provision for income taxes is as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Provision (benefit) at U.S. federal statutory rate	$	(109,302)	$	37,591	$	2,645
Unbenefited net operating losses and tax credits		(99,254)		(47,410)		(29,424)
Non-deductible amortization of debt discount		—		—		1,087
Excess tax benefits related to share-based compensation		(81,021)		(29,541)		—
Deferred tax impact of Tax Cuts and Jobs Act of 2017		196,751		—		—
Foreign tax rate differential		86,777		39,975		21,443
Non-deductible officer compensation		6,351		2,061		4,696
Other		550		506		578
Provision for income taxes	$	852	$	3,182	$	1,025

The foreign tax rate differential in the table above reflects the impact of operations in jurisdictions with tax rates that differ from the U.S. federal statutory rate.

Significant components of our deferred tax assets and liabilities are as follows (in thousands):


	December 31,
	2017		2016
Deferred tax assets:
Net operating loss carry forwards	$	259,189	$	481,155
Federal and state research credits		333,311		250,324
Capitalized research and development		37,044		18,618
Deferred revenue and accruals		11,721		9,882
Non-cash compensation		44,647		56,370
Contingent consideration		41,831		32,500
Intangibles, net		94,249		—
Other		25,724		19,533
Total gross deferred tax assets		847,716		868,382
Less valuation allowance for deferred tax assets		(834,783)		(820,233)
Net deferred tax assets	$	12,933	$	48,149

Deferred tax liabilities:
Property and equipment	$	(11,463)	$	(7,761)
Intangibles, net		—		(5,337)
Equity component of 2018 Notes and 2020 Notes		(665)		(35,051)
Total gross deferred tax liabilities		(12,128)		(48,149)
Net deferred income taxes	$	805	$	—

As of December 31, 2017, the Company has NOL carryforwards, research and development credit carryforwards and orphan drug tax credit carryforwards as follows (in thousands):


	Amount		Expiring if not utilized
Net operating loss carryforwards
Federal	$	862,876	2024 through 2037
State		504,535	2024 through 2037
Foreign		420,725	2020 through 2024
Research and development credit carryforwards
Federal		154,135	2018 through 2037
State		21,577	Indefinite
Orphan drug tax credit carryforwards		181,480	2029 through 2037

Our ability to utilize our federal and state NOLs may be limited under Internal Revenue Code Section 382 (“Section 382”). Section 382 imposes annual limitations on the utilization of NOL carryforwards and other tax attributes upon an ownership change. In general terms, an ownership change may result from transactions that increase the aggregate ownership of certain stockholders in our stock by more than 50 percentage points over a testing period (generally three years). We have completed a Section 382 analysis through the year ended December 31, 2017. Based on this analysis, our NOLs and other tax attributes accumulated through 2017 should not be limited under Section 382.

On December 22, 2017, the Tax Cuts and Jobs Act of 2017 was signed into law making significant changes to the Internal Revenue Code. The Act contains numerous provisions impacting corporate taxpayers. Changes include a federal corporate tax rate decrease from 35% to 21% effective for tax years beginning after December 31, 2017, the transition of U.S. international taxation from a worldwide tax system to a territorial system and temporary full expensing of certain business assets. We have recorded provisional tax impacts related to the revaluation of deferred tax assets and liabilities as well as the temporary full expensing of certain business assets in our consolidated financial statements for the year ended December 31, 2017. The ultimate impact may differ from these provisional amounts, due to additional analysis, changes in interpretations and assumptions, and additional regulatory guidance that may be issued. The financial statement impact is expected to be complete when the 2017 U.S. corporate income tax return is filed in 2018.

The valuation allowance for deferred tax assets increased by approximately $14.6 million during the year ended December 31, 2017, increased by approximately $277.3 million during the year ended December 31, 2016 and decreased by approximately $126.2 million during the year ended December 31, 2015. Upon enactment of the Act, the Company remeasured its U.S. deferred tax assets and liabilities at the applicable tax rate of 21%. The remeasurement resulted in a total decrease in these net assets of $197.0 million, which was fully offset by a corresponding valuation allowance reduction.

Valuation allowances require an assessment of both positive and negative evidence when determining whether it is more likely than not that deferred tax assets are recoverable. Such assessment is required on a jurisdiction-by-jurisdiction basis. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible.

Based upon the Company’s analysis of its historical operating results, as well as projections of the Company’s future taxable income (losses) during the periods in which the temporary differences will be recoverable, management believes the uncertainty regarding the realization of its U.S. and Swiss net deferred tax assets requires a full valuation allowance against such net assets as of December 31, 2017. When performing our assessment on projections of future taxable income (losses), we consider factors such as the likelihood of regulatory approval and commercial success of products currently under development, among other factors.

The financial statement recognition of the benefit for a tax position is dependent upon the benefit being more likely than not to be sustainable upon audit by the applicable taxing authority. If this threshold is met, the tax benefit is then measured and recognized at the largest amount that is greater than 50% likely of being realized upon ultimate settlement. If such unrecognized tax benefits were realized and not subject to valuation allowances, we would recognize a tax benefit of $18.0 million. The following table summarizes the gross amounts of unrecognized tax benefits (in thousands):


	Year Ended December 31,
	2017		2016
Balance at beginning of year	$	10,798	$	836
Additions related to prior periods tax positions		2,571		6,740
Reductions related to prior periods tax positions		(821)		—
Additions related to current period tax positions		5,555		2,652
Acquisitions		—		570
Reductions due to lapse of applicable statute of limitations		(81)		—
Balance at end of year	$	18,022	$	10,798

Our policy is to recognize interest and penalties related to uncertain tax positions, if any, as a component of income tax expense. As of December 31, 2017 and 2016, we accrued interest and penalties of $0.3 million. Due to NOL and tax credit carry forwards that remain unutilized, U.S. federal and state income tax returns remain subject to examination for three years after utilization of that year’s NOL carryforward. The earliest year which generated an NOL included in our current NOL carryforward is 2004 for U.S. federal tax purposes. All tax years for our foreign subsidiaries are open to audit in their respective jurisdictions.