There was no provision for income taxes recorded for the years ended December 31, 2020 and 2019. The Company continues to maintain a full valuation allowance against its net deferred tax assets due to the uncertainty surrounding realization of such assets. The Company periodically evaluates the realizability of its net deferred tax assets based on the expected realization and is dependent on the Company's ability to generate sufficient future taxable income during periods prior to the expiration of tax attributes to fully utilize these assets.


	Year ended December 31,
	2020		2019
	(in thousands)
Federal	$	9,855	$	8,523
State	2,711		1,569
Foreign	583		(200)
Total deferred income taxes	13,149		9,892
Change in deferred tax valuation allowance	(13,149)		(9,892)
Net deferred income tax	$	—	$	—


	Year ended December 31,
	2020		2019
Tax at statutory federal rate	(21.0)	%	(21.0)	%
State tax, net of federal benefit	(6.2)	%	(4.1)	%
Tax credits	(0.7)	%	(0.7)	%
Change in deferred tax valuation allowance	30.1	%	25.8	%
Stock compensation	(1.2)	%	(1.5)	%
Foreign rate differences	(1.3)	%	0.5	%
Other	0.3	%	1.0	%
Total income tax expense	—	%	—	%


	Year ended December 31,
	2020		2019
	(in thousands)
Net operating loss carryforwards	$	52,331	$	42,032
Research and development credits	3,160		2,428
Accruals and reserves	5,450		4,222
Stock compensation	2,395		1,512
Depreciation and amortization	117		110
Total deferred tax assets	63,453		50,304
Less: Valuation allowance	(63,453)		(50,304)
Total deferred tax asset, net of valuation allowance	$	—	$	—

As of December 31, 2020, the Company had net operating loss (“NOL”) carryforwards of approximately $200.5 million and $165.0 million available to reduce future taxable income, if any, for federal and state income tax purposes, respectively. If not utilized, the Company’s federal NOL carryforward begins to expire in 2028, and the state NOL carryforward begins to expire in 2021.

As of December 31, 2020, the Company had credit carryforwards of approximately $2.5 million and $2.5 million available to reduce future taxable income, if any, for both federal and state income tax purposes, respectively. The federal credits begin to expire in 2029, and the state credits have no expiration date.

The Company updated its Section 382 ownership change analysis through December 31, 2020 and determined that the last ownership change was in February 2020 due to the follow-offering. The analysis concluded that no additional NOL carryforwards will expire due to the Section 382 limitation from the ownership change for both federal and state tax purposes. The Company maintains the reduction of $1.4 million of its NOL carryforwards from the previous ownership change. The Company will continually assess the need to update its Section 382 ownership change analysis, as the Company may experience ownership changes in the future that could materially limit its ability to use its NOL carryforwards.

The CARES Act includes provisions relating to refundable payroll tax credits, deferment of employer's social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property. The Company deferred the payment of an employer's share of social security taxes through December 31, 2020 of $1.0 million.

On June 29, 2020, Governor Gavin Newsom signed California Assembly Bill 85 (AB 85) into law. The legislation suspends the California net operating loss deductions for 2020, 2021, and 2022 for certain taxpayers and imposes a limitation of certain California Tax Credits for 2020, 2021, and 2022. The legislation disallows the use of California net operating loss deductions if the taxpayer recognizes business income and its adjusted gross income is greater than $1.0 million. The carryover periods for net operating loss deductions disallowed by this provision will be extended. Additionally, any business credit will only offset a maximum of $5.0 million of California tax. Given the Company’s loss position for the year ended December 31, 2020, the new legislation did not impact the current year provision. The Company will continue to monitor the possible California net operating loss and credit limitations in future periods.

The Company accounts for the uncertainty in income taxes by utilizing a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of any uncertain tax positions that have been taken or are expected to be taken on an income tax return. The changes in the Company’s uncertain income tax positions for the years ended December 31, 2020 and 2019 consisted of the following:


	Year ended December 31,
	2020		2019
	(in thousands)
Balance at beginning of the year	$	1,287	$	1,084
Increases related to current year's tax positions	226		203
Balance at end of the year	$	1,513	$	1,287

The Company has elected to recognize interest and penalties related to uncertain tax positions as a component of income tax expense. The Company has no accrued interest related to unrecognized tax benefits as of December 31, 2020 and 2019. None of the Company’s unrecognized tax benefits that, if recognized, would affect its effective tax rates for the years ended December 31, 2020 and 2019. The Company does not anticipate the total amounts of unrecognized tax benefits will significantly increase or decrease in the next 12 months.

The Company currently has no federal, state or foreign tax examinations in progress nor has it had any federal or state examinations since inception. As a result of the Company’s net operating loss carry forwards, all of its tax years are subject to federal and state tax examinations.