Income tax benefit differed from the amount computed by applying the federal blended statutory income tax rate of 21% to pretax loss as a result of the following (in thousands):

	Fiscal Year Ended January 31,
	2019			Rate			2018			Rate			2017			Rate
Federal tax at statutory rate	$	(3,141	)		21	%	$	(4,316	)		33	%	$	(4,403	)		34	%
Impact of U.S. tax law change		58			—			11,667			(89	)%		—			—
Change in valuation allowance		5,603			(37	)%		(6,786	)		52	%		4,881			(38	)%
Research and development credit		(2,155	)		14	%		(1,080	)		8	%		(738	)		6	%
State taxes		(494	)		3	%		(396	)		3	%		(230	)		2	%
Stock-based compensation		(991	)		7	%		387			(3	)%		387			(3	)%
Permanent tax adjustment		843			(6	)%		527			(4	)%		103			(1	)%
Impact of foreign operations		(105	)		1	%		—			—			—			—
Other		(2	)		—			—			—			—			—
Total	$	(384	)		(3	)%	$	3			0	%	$	—			0	%

Income tax expense differs from the amount computed by applying the statutory federal income tax rate primarily as the result of changes in the valuation allowance.

The tax effects of temporary differences that give rise to significant portions of the Company’s deferred tax assets and liabilities related to the following (in thousands):

	As of January 31,
	2019			2018
Deferred tax assets:
Accruals and reserves	$	1,549		$	2,281
Stock-based compensation		1,071			1,030
Intangible assets amortization		(21	)		61
Deferred revenue		73			125
Net operating loss carry forwards		26,277			22,047
Tax credit carryover		5,977			3,810
Gross deferred tax assets		34,926			29,354
Valuation allowance		(34,309	)		(28,657	)
Net deferred tax assets	$	617		$	697
Deferred tax liabilities:
Acquired intangible assets	$	(607	)	$	(313	)
Fixed assets depreciation		(154	)		(384	)
Gross deferred tax liabilities	$	(761	)	$	(697	)
Total deferred tax liabilities	$	(144	)	$	—

On December 22, 2017, the Tax Cuts and Jobs Act (“Tax Act”) was enacted, reducing the corporate income tax rate from 35% to 21%, effective January 1, 2018. The carrying value of the Company's deferred tax assets was also determined by the enacted U.S. corporate income tax rate. Consequently, any changes in the U.S. corporate income tax rate have impacted the carrying value of the Company’s deferred tax assets. Under the new corporate income tax rate of 21%, deferred income taxes decreased, with a corresponding decrease to the valuation allowance. Therefore, the Tax Act had no impact on the Company's fiscal 2019 net loss. As of January 31, 2019, the Company has completed its accounting of the tax effects from the enactment of the Tax Act.

The Company has a Section 162(m) stock awards limitation on deferred tax assets of $0.1 million. Effective for tax years beginning on January 1, 2018 or later, which is considered fiscal 2019 for the Company, tax reform legislation modifies Section 162(m) rules to repeal the performance-based compensation and commission exceptions to the $1.0 million deduction limitation. However, written binding contracts in effect on November 2, 2017, including plans where the right to participate in the plan is part of a written contract with an executive, are grandfathered and not subject to limitation under Section 162(m). The Company believes some of its contracts will not be subject to limitation and will continue to monitor the deferred tax assets related to deferred compensation expense and share-based compensation expense on a going forward basis.

Management believes that, based on available evidence, both positive and negative, it is more likely than not that the deferred tax assets will not be utilized, such that a full valuation allowance has been recorded. The valuation allowance for deferred tax assets was $34.3 million, $28.7 million and $34.9 million as of January 31, 2019, 2018 and 2017, respectively. The net change in the total valuation allowance for fiscal 2019 and 2018 was an increase of $5.7 million and a decrease of $6.2 million, respectively.

As of January 31, 2019, the Company had approximately $99.0 million and $71.8 million of net operating loss (“NOL”) carryforwards available to offset future taxable income for both federal and state purposes, respectively. If not utilized, these available carryforward losses will expire in various amounts for federal and state tax purposes beginning in 2030. In addition, the Company had approximately $5.8 million and $5.2 million of federal and state research and development tax credits, respectively, available to offset future taxes. If not utilized, the available federal credits will begin to expire in 2030. California state research and development tax credits can be carried forward indefinitely.

The Company has unrecognized tax benefits (“UTBs”) of approximately $4.4 million as of January 31, 2019. Deferred tax assets associated with these UTBs are fully offset by a valuation allowance. If recognized, these UTBs would not affect the effective tax rate before consideration of the valuation allowance. The following table summarizes the activity related to UTBs (in thousands):

The UTBs reported above, if recognized, would not affect the effective tax rate before consideration of the valuation allowance. The Company had no interest or penalty accruals associated with uncertain tax benefits in its balance sheets and statements of operations for both fiscal 2019 and 2018. The Company does not have any tax positions for which it is reasonably possible the total amount of gross unrecognized benefits will increase or decrease within 12 months of the year ended January 31, 2019. Because the Company has net operating loss and credit carryforwards, there are open statutes of limitations in which federal, state and foreign taxing authorities may examine the Company’s tax returns for all years from 2009 through the current period.