A reconciliation of the differences between the United States statutory federal income tax rate and the effective tax rate as provided in the statements of operations is as follows:

	Year Ended December 31,
	2019			2018
Tax computed at the federal statutory rate		21.0	%		21.0	%
State income taxes, net of federal benefits		1.9			2.7
Nondeductible expenses		(0.4	)		(2.0	)
Stock-based compensation		(9.5	)		(2.2	)
Change in valuation allowance		(13.0	)		(19.5	)
		—			—

The federal and state income tax provision is summarized as follows (in thousands):

	Year Ended December 31,
	2019		2018
Current
Federal	$	—	$	—
State		15		10
		15		10
Deferred
Federal		—		—
State		—		—
		—		—
Income tax expense	$	15	$	10

Deferred income taxes reflect the net tax effects of (a) temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for tax purposes, and (b) operating losses and tax credit carryforwards.

The tax effects of significant components of the Company’s deferred tax assets (liabilities) are as follows (in thousands):

	December 31,
	2019			2018
Deferred Tax Assets:
Net operating loss carryforwards	$	16,096		$	6,990
Operating lease liabilities		766			—
Other accruals		61			88
Reserves		301			203
Deferred revenue		850			661
Intangible assets		253			353
Stock-based compensation		4,821			6,464
Total gross deferred tax assets	$	23,148		$	14,759
Deferred Tax Liabilities:
Property and equipment		(1,026	)		(888	)
Operating lease right-of-use assets		(739	)		—
Other		(92	)		—
Total gross deferred tax liabilities	$	(1,857	)	$	(888	)
Valuation allowance		(21,291	)		(13,871	)
Total deferred taxes	$	—		$	—

At December 31, 2019, the Company had available federal and state net operating loss carryforwards of approximately $63.7 million and $66.0 million, respectively, which may be used to offset future federal and state taxable earnings. The federal and state net operating losses begin expiring in 2029. Use of these net operating loss carryforwards may be significantly limited under the tax rules regarding the use of losses following an ownership change under Internal Revenue Code (“IRC”) Section 382. The Company has completed an IRC Section 382 analysis regarding the limitation of net operating losses through June 30, 2019 and has determined that no ownership change has occurred.

As of December 31, 2019, the Company does not have any unrecognized tax benefits. The Company does not anticipate that the amount of unrecognized tax benefits will significantly increase in the next 12 months. There were no interest and penalties accrued as of December 31, 2019. The Company files U.S. federal and various states income tax returns, which are subject to examination by the taxing authorities for years 2015 and later. However, the federal net operating loss carryover may be adjusted three years from the date the loss is utilized on an income tax return.

ASC 740, Income Taxes, requires that the tax benefit of net operating losses, temporary differences and credit carryforwards be recorded as an asset to the extent that management assesses that realization is “more likely than not.” Realization of the future tax benefits is dependent on the Company’s ability to generate sufficient taxable income within the carryforward period. Because of the Company’s recent history of operating losses, management believes that recognition of the deferred tax assets arising from the above-mentioned future tax benefits is not currently more likely than not to be realized and, accordingly, has provided a full valuation allowance at December 31, 2019 and 2018.