On December 22, 2017, the 2017 Tax Act was enacted into law. Beginning January 1, 2018, the 2017 Tax Act reduced the U.S. federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax-deferred, created new taxes on certain foreign sourced earnings, repealed the Alternative Minimum Tax (“AMT”), and expanded the number of individuals whose compensation is subject to a $1.0 million cap on deductibility, amongst other minor changes.

In January 2018, the SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“SAB 118”) which allowed companies to report provisional amounts as it related to the 2017 Tax Act based on reasonable estimates for items for which the accounting was incomplete during a measurement period that lapsed in the fourth quarter of 2018. During the year ended December 31, 2017, we recorded a provisional tax benefit of $2.4 million related to the remeasurement of our deferred tax assets and liabilities, net of valuation allowance, to reflect the reduction in the corporate tax rate and $2.6 million related to refundable AMT credits generated by the Company in previous years. During the year ended December 31, 2018, there was no net impact to the provision for income taxes based on adjustments made to the provisional amounts recorded during the previous year. However, the Company did record a provision for income tax expense of $3.9 million during the year ended December 31, 2018 related to the Base Erosion and Anti-Abuse Tax (“BEAT”) as a result of proposed regulations issued by the United States Treasury Department. The Company completed its accounting for the income tax effects of the 2017 Tax Act during 2018.

Income (loss) before income taxes consists of the following for the periods shown below (in thousands):

	Year Ended December 31,
	2019			2018			2017
United States	$	155,887		$	29,941		$	(6,081	)
International		(108,552	)		(3,478	)		43,664
Total	$	47,335		$	26,463		$	37,583

The provision for (benefit from) income taxes consists of the following for the periods shown below (in thousands):

	Year Ended December 31,
	2019			2018			2017
Current tax expense (benefit):
Federal	$	11,552		$	3,918		$	(2,132	)
State		5,387			205			142
Foreign		7,722			11,967			13,562
Total current tax expense (benefit)	$	24,661		$	16,090		$	11,572
Deferred tax (benefit) expense:
Federal	$	90		$	1,350		$	(1,231	)
State		560			444			300
Foreign		(19,901	)		(6,878	)		303
Total deferred tax (benefit) expense	$	(19,251	)	$	(5,084	)	$	(628	)
Provision for (benefit from) income taxes	$	5,410		$	11,006		$	10,944

The reconciliation of federal statutory income tax provision (benefit) to our effective income tax provision is as follows (in thousands):

	Year Ended December 31,
	2019			2018			2017
Expected provision for (benefit from) income taxes at U.S. federal statutory rate⁽¹⁾	$	9,940		$	5,557		$	13,154
State income taxes, net of federal benefit		4,743			205			142
BEAT obligation		—			3,918			—
Income (loss) taxed at foreign rates		10,292			4,447			(3,643	)
Stock-based compensation		(15,683	)		(3,457	)		(2,898	)
Tax reserve for uncertain tax positions		3,174			1,676			3,101
Change in valuation allowance		(56,194	)		(5,610	)		(51,976	)
Impact of 2017 Tax Act		—			—			48,237
Acquisition costs		1,166			536			—
Contingent consideration		42,328			1,155			(252	)
Officer's compensation limitation		5,165			2,340			2,582
Investment in subsidiaries		—			—			1,676
Other		479			239			821
Actual provision for (benefit from) income taxes	$	5,410		$	11,006		$	10,944

Our analysis of the one-time transition tax liability for our foreign subsidiaries enacted by the 2017 Tax Act did not result in additional taxes being owed, considering our accumulated deficit position at December 31, 2017. Additionally, no other income taxes (state or foreign) have been provided for any remaining undistributed foreign earnings not subject to the transition tax, or any additional outside basis difference inherent in our foreign subsidiaries, as these amounts continue to be indefinitely reinvested in foreign operations. As of December 31, 2019 and 2018, the cumulative amount of earnings upon which income taxes have not been provided is approximately $87.1 million and $73.0 million, respectively.

Deferred tax assets and liabilities are recognized for the future tax consequences of differences between the carrying amounts of assets and liabilities and their respective tax basis using enacted tax rates in effect for the year in which the differences are expected to be reversed. Our deferred tax assets and liabilities are as follows (in thousands):

	December 31,			December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	35,546		$	60,737
Tax credit carryforwards		76,354			103,740
Operating lease liabilities		34,382			—
Acquired intangible assets		29,982			28,957
Stock-based compensation		9,251			10,150
Accrued expenses		4,899			3,718
Other accrued compensation		7,297			6,524
Charitable contributions		67			2,533
State taxes		1,547			351
Other		71			—
Total deferred tax assets	$	199,396		$	216,710
Less: Valuation allowance		(141,577	)		(205,989	)
Deferred tax assets, net of valuation allowance	$	57,819		$	10,721

Deferred tax liabilities:
Acquired intangible assets	$	(37,600	)	$	(11,637	)
Right-of-use assets		(34,021	)		—
Goodwill		(7,131	)		(5,000	)
Deferred rent		—			(2,334	)
Depreciation		—			(4,694	)
Convertible debt		(9,621	)		—
Other		(2,275	)		(2,547	)
Total deferred tax liabilities	$	(90,648	)	$	(26,212	)
Net deferred taxes	$	(32,829	)	$	(15,491	)

Due to our history of net operating losses, we believe it is more likely than not that certain federal, state and foreign deferred tax assets will not be realized in future periods as of December 31, 2019. The decrease in the valuation allowance during the year ended December 31, 2019 is primarily related to the use of net operating losses to offset taxable income in 2019, mainly associated with the Building Sale.

Net operating loss and tax credit carryforwards as of December 31, 2019 are as follows (in thousands):

The federal and state net operating loss carryforwards are subject to various annual limitations under Section 382 of the Internal Revenue Code and similar state provisions.

The following table reflects changes in the gross unrecognized tax benefits (in thousands):

December 31, 2016	$	151,100
Additions based on tax positions related to 2017		8,598
Additions for tax positions of prior years		427
Decreases related to expiration of prior year tax positions		(31	)
Decreases related to settlements of prior year tax positions		(54	)
December 31, 2017	$	160,040
Additions based on tax positions related to 2018		4,355
Additions for tax positions of prior years		815
Decreases related to expiration of prior year tax positions		(1,230	)
December 31, 2018	$	163,980
Additions based on tax positions related to 2019		5,879
Additions for tax positions of prior years		1,888
Decreases related to expiration of prior year tax positions		(322	)
December 31, 2019	$	171,425

We classify uncertain tax positions as non-current unrecognized tax liabilities unless expected to be paid within one year or otherwise directly related to an existing deferred tax asset, in which case the uncertain tax position is recorded as an offset to the asset on the consolidated balance sheet. As of December 31, 2019, $156.6 million of our gross unrecognized tax benefits were recorded as a reduction of the related deferred tax assets and the remaining $14.8 million of our gross unrecognized tax benefits were recorded as non-current liabilities in our consolidated balance sheets.

If the balance of gross unrecognized tax benefits of $171.4 million as of December 31, 2019 was realized, this would have resulted in a tax benefit of $14.8 million within our provision for income taxes at such time. If the balance of gross unrecognized tax benefits of $164.0 million as of December 31, 2018 was realized, this would have resulted in a tax benefit of $9.2 million within our provision of income taxes at such time.

During all years presented, we recognized interest and penalties related to unrecognized tax benefits within the provision for income taxes on the consolidated statements of operations. The amount of interest and penalties recorded to the consolidated statements of operations during 2019, 2018 and 2017, was $0.2 million, $0.2 million and $0.3 million, respectively, and the amount of interest and penalties accrued as of December 31, 2019 and 2018 was $1.1 million and $0.9 million, respectively.

We file income tax returns in the U.S. federal jurisdiction as well as many U.S. states and certain foreign jurisdictions. The material jurisdictions in which we are subject to potential examination include the U.S., United Kingdom, Ireland and Finland. We are subject to examination in these jurisdictions for all years since our inception in 2007. Fiscal years outside the normal statute of limitation remain open to audit by tax authorities due to tax attributes generated in those early years which have been carried forward and may be audited in subsequent years when utilized. We do not expect any material changes to our unrecognized tax benefits within the next twelve months.

On June 7, 2019 the U.S. Court of Appeals for the Ninth Circuit (“Ninth Circuit”), issued an opinion in Altera Corp v. Commissioner reversing a 2015 U.S. Tax Court decision. The Ninth Circuit ruled in favor of the Commissioner, validating U.S. Treasury regulations that require parties to a qualified cost-sharing arrangement to include stock-based compensation in the cost pool. Altera Corp subsequently petitioned the Ninth Circuit for a rehearing en banc, and, on November 12, 2019, the Ninth Circuit denied such petition. On February 10, 2020, Altera Corp requested the U.S. Supreme Court to review the Ninth Circuit’s decision. It is unclear whether the U.S. Supreme Court will review the case or when a determination will be made. As a result, the final outcome of the case is uncertain. Due to the uncertainty surrounding the status of the current regulations, questions related to the scope of potential benefits or obligations, and the possibility of the Ninth Circuit’s decision being overturned upon appeal, we have not recorded a liability related to an unrecognized tax position as of December 31, 2019. We will continue to monitor future developments and their potential effects on our consolidated financial statements.