	Year Ended December 31,
(in thousands)	2020			2019			2018
Current
Federal	$	235		$	20,012		$	10,368
State		848			2,592			620
		1,083			22,604			10,988
Deferred
Federal		(7,472	)		(4,670	)		(1,789	)
State		(3,438	)		(1,004	)		(644	)
		(10,910	)		(5,674	)		(2,433	)
Total income tax (benefit) expense	$	(9,827	)	$	16,930		$	8,555

The reconciliation of the income tax (benefit) expense computed at the U.S. Federal statutory rate of 21% to the Company's income tax (benefit) expense is as follows:

	Year Ended December 31,
(in thousands)	2020			2019			2018
Income taxes computed at Federal statutory rate	$	(63,725	)	$	17,425		$	10,993
State income taxes		(2,768	)		988			(154	)
Stock-based compensation		609			313			(99	)
Excess tax benefits related to stock- based compensation		(19,961	)		(788	)		(1,276	)
Research and development credits		(3,541	)		(1,661	)		(858	)
Nondeductible officers' compensation		79,046			—			—
(Decrease) increase in valuation allowance		(293	)		380			—
Other		806			273			(51	)
Income tax (benefit) expense	$	(9,827	)	$	16,930		$	8,555
Effective income tax rate		3.2	%		20.4	%		16.3	%

	December 31,
(in thousands)	2020			2019
Deferred tax assets
Other assets	$	2,303		$	3,108
Lease liabilities		8,747			9,111
Stock-based compensation		4,422			840
Research and development credits, net of reserves		4,146			1,845
Tax credit carryforward		296			—
Charitable contribution carryforward		8,403			—
Goodwill		9,329			2,524
Net operating losses		215			570
Total deferred tax assets		37,861			17,998
Valuation allowance		(268	)		(561	)
Deferred tax assets, net of valuation allowance		37,593			17,437
Deferred tax liabilities
Other liabilities		(825	)		(214	)
Lease assets		(6,377	)		(9,002	)
Property and equipment		(4,621	)		(335	)
Capitalized software		(4,557	)		(1,072	)
Intangible assets		(8,096	)		(4,607	)
Total deferred tax liabilities		(24,476	)		(15,230	)
Net deferred tax assets	$	13,117		$	2,207

The Company regularly reviews its deferred tax assets for recoverability and establishes a valuation allowance when it is more likely that some portion, or all, of the deferred tax assets will not be realized. In making the assessment, the Company is required to consider all available positive and negative evidence to determine whether, based on such evidence, it is more likely than not that some portion or all of the net deferred tax assets will not be realized in future periods. At December 31, 2020, the Company has recorded a valuation allowance of $0.3 million for certain deferred tax assets, primarily related to U.S. net operating loss carryforwards ("NOLs") generated by the Professional Service Corporations (“PSCs”) as sufficient uncertainty exists regarding the future realization of these assets.

On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) was signed into law, featuring significant tax provisions and other measures to assist individuals and businesses impacted by the economic effects of the COVID-19 pandemic. The CARES Act increased the Section 163(j) interest expense deduction limitation from 30% to 50% of adjusted taxable income, provided for the payment deferral of certain Social Security taxes, made a technical correction allowing Qualified Improvement Property to be treated as 15-year property, and included numerous other provisions. The CARES Act increased the Company’s interest expense deduction applicable to the 2019 tax year resulting in a reduction of deferred tax assets and a corresponding reduction in income taxes payable of approximately $2.3 million during the quarter ended March 31, 2020.

At December 31, 2020, the Company had U.S. NOLs of $2.9 million available to reduce future federal income taxes. An immaterial portion of these federal NOLs expire in 2037 and the remaining NOLs may be carried over indefinitely. The Company had state NOLs of $1.3 million available to reduce future state income taxes which expire in varying amounts beginning 2029. In 2020, there was a change in ownership of the PSCs. Section 382 of the Internal Revenue Code (“IRC”) limits the utilization of U.S. NOLs following a change of control. As the 2020 change in ownership in the PSCs constitutes a change of control, the Company estimates that approximately $2.2 million of its U.S. NOLs carryforward generated by the PSCs are limited by Section 382. Any adjustment to the estimated Section 382 limitation would not be material to the consolidated financial statements as a full valuation allowance has been established against the NOLs from the PSCs due to uncertainty regarding their future realization.

The Company had California Competes tax credit carryforwards in the amount of $0.4 million available to offset future California income taxes as of December 31, 2020. Under current California law, unused California Competes tax credits may be carried forward for up to six years. At December 31, 2020, the Company also had California research and development tax credit carryforwards in the amount of $7.8 million to offset future California income taxes. Unused California research credits may be carried forward indefinitely. Utilization of these tax credits may be subject to an annual limitation based on changes in ownership, as defined by Section 382/383 of the IRC, as amended.

At December 31, 2020, the tax years 2017 and forward are subject to examination by the IRS, and the tax years 2016 and forward are subject to examination by the various state taxing jurisdictions in which the Company is subject to tax. Currently, income tax audits are occurring in the state of New York and Illinois.

A reconciliation of the beginning and ending amount of gross unrecognized tax benefits is as follows:

(in thousands)
Gross unrecognized tax benefits at December 31, 2017	$	865
Increases related to prior year tax positions		458
Increases related to current year tax positions		3,186
Gross unrecognized tax benefits at December 31, 2018		4,509
Decreases related to prior year tax positions		(879	)
Increases related to current year tax positions		744
Gross unrecognized tax benefits at December 31, 2019		4,374
Increases related to prior year tax positions		126
Increases related to current year tax positions		3,327
Settlements with taxing authorities		(119	)
Lapse of statute of limitations		(317	)
Gross unrecognized tax benefits at December 31, 2020	$	7,391

As of December 31, 2020, the Company had unrecognized tax benefits of $7.4 million, $6.7 million of which, if recognized, would impact its effective tax rate.

The Company estimates unrecognized tax benefits will decrease by $0.5 million in 2021 due to the expiration of statute of limitations.

At December 31, 2020 and 2019, accrued interest and penalties related to uncertain tax positions were $0.2 million and $0.1 million, respectively.