	Year Ended December 31,
	2018			2017			2016
	(in thousands)
Domestic	$	(41,985	)	$	(16,642	)	$	(8,572	)
Foreign		(4,734	)		(2,945	)		(2,738	)
Total	$	(46,719	)	$	(19,587	)	$	(11,310	)

For purposes of reconciling the Company’s provision for income taxes at the statutory rate and the Company’s provision (benefit) for income taxes at the effective tax rate, a notional 26% tax rate was applied as follows:

	Year Ended December 31,
	2018			2017			2016
	(in thousands)
Income tax at federal statutory rate	$	(9,811	)	$	(6,659	)	$	(3,846	)
Increase/(decrease) in tax resulting from:
State income tax expense, net of federal tax effect		(2,749	)		(421	)		(183	)
Nondeductible permanent items		(1,522	)		1,506			1,012
Foreign rate differential		552			599			662
Tax rate change		134			7,226			(13	)
Adjustment to deferred taxes		307			37			(132	)
Change in valuation allowance		15,805			(2,291	)		2,351
Uncertain tax positions		143			76			83
Nonqualified stock option and performance award windfall upon exercise		(1,983	)		—			—
Other		(80	)		(26	)		42
Total	$	796		$	47		$	(24	)

The difference between the statutory federal income tax rate and the Company’s effective tax rate in 2018, 2017 and 2016 is primarily attributable to the effect of state income taxes, difference between the U.S. and foreign tax rates, deferred tax state rate adjustment, share-based compensation and other non-deductible permanent items, and the change in valuation allowance. The Company’s China, India, Norway, Netherlands, Sweden and U.K. subsidiaries were subject to 25%, 30%, 22%, 25%, 22% and 19% applicable statutory income tax rates, respectively, for the periods presented.

	Year Ended December 31,
	2018			2017			2016
	(in thousands)
Current:
Federal	$	—		$	(23	)	$	—
State		48			51			31
Foreign		753			31			109
		801			59			140
Deferred:
Federal		(11,425	)		3,307			(1,823	)
State		(3,250	)		(669	)		(396	)
Foreign		(1,135	)		(359	)		(296	)
		(15,810	)		2,279			(2,515	)
Change in valuation allowance		15,805			(2,291	)		2,351
Total	$	796		$	47		$	(24	)

The net deferred tax assets (liabilities) at December 31, 2018 and 2017 are comprised of the following:

	As of December 31,
	2018			2017
	(in thousands)
Deferred tax assets
Deferred rent	$	278		$	133
AMT credit		11			9
Accrued expenses		2,057			1,474
Deferred revenue		549			292
Net operating loss carryforward		34,662			14,957
Other assets		2,343			1,643
Property and equipment		123			—
Intangible assets		836			—
Valuation allowance		(25,079	)		(10,911	)
Total net deferred tax assets		15,780			7,597
Deferred tax liabilities
Deferred commissions		(3,215	)		—
Intangible assets		(7,295	)		(2,210	)
Property and equipment		—			(190	)
Debt discount		(4,986	)		(5,679	)
Other		(1,233	)		—
Total deferred tax liabilities		(16,729	)		(8,079	)
Total non-current deferred income tax liabilities	$	(949	)	$	(482	)

A valuation allowance is recorded to reduce deferred tax assets to the amount that is more likely than not to be realized based on an assessment of positive and negative evidence, including estimates of future taxable income necessary to realize future deductible amounts. A significant piece of objective negative evidence evaluated was the cumulative loss incurred over the three-year period ended December 31, 2018. Such objective evidence limits the ability to consider other subjective evidence such as its projections for future growth. On the basis of this evaluation, at December 31, 2018 and 2017, a valuation allowance of $25.1 million and $10.9 million, respectively, has been recorded.

As of December 31, 2018, the Company has accumulated federal and state net operating loss carryforwards of $104.8 million and $85.7 million, respectively. Of the $104.8 million of federal net operating loss carryforwards, $52.1 million was generated before January 1, 2018 and is subject to the 20-year carryforward period (“pre-Tax Act losses”). The remaining $52.7 million (“post-Tax Act losses”) can be carried forward indefinitely but is subject to the 80% taxable income limitation. The pre Tax Act U.S. federal and state net operating loss carryforwards will expire in varying amounts through 2037. Section 382 of the Internal Revenue Code, or Section 382, imposes limitations on a corporation’s ability to utilize its Net Operating Losses, or NOLs, if it experiences an “ownership change.” In general terms, an ownership change may result from transactions increasing the ownership percentage of certain stockholders in the stock of the corporation by more than 50% over a three-year period. In the event of an ownership change, utilization of the NOLs would be subject to an annual limitation under Section 382 determined by multiplying the value of the Company’s stock at the time of the ownership change by the applicable long-term tax exempt rate. The Company has not completed a Section 382 study at this time; however should a study be completed certain NOLs may be subject to such limitations. Any future annual limitation may result in the expiration of NOLs before utilization.

As of December 31, 2018 and 2017, the Company had combined foreign net operating loss carry-forwards available to reduce future taxable income of approximately $25.5 million and $4.6 million, respectively. As of December 31, 2018 and 2017, valuation allowances of $25.1 million and $4.5 million, respectively, had been recorded against the related deferred tax assets for those loss carry-forwards that are not more likely than not to be fully utilized in reducing future taxable income.

On December 22, 2017, the United States government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act, or the Tax Act. The Tax Act significantly revises the existing tax law by, among other things, lowering the United States corporate income tax rate from 35% to 21% beginning in 2018. The SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“SAB 118”), which allows companies to record provisional amounts during a measurement period not to extend beyond one year of the enactment date.

The Company reviewed and incorporated the impact of the Tax Act in its tax calculations and disclosures. The primary impact on the Company stems from the re-measurement of its deferred taxes at the new corporate tax rate of 21%, which reduced the Company's net deferred tax assets, before valuation allowance, by $7.2 million. Due to the full valuation allowance, the change in deferred taxes was fully offset by the change in valuation allowance, except for an immaterial amount that was reflected in income tax expense related to the rate re-measurement of the tax-deductible goodwill. The accounting for the Act is now complete and no significant adjustments were made to the provisional estimates. The Tax Act did not have a significant impact on the Company's Consolidated Financial Statements for the year ended December 31, 2018.

The following changes occurred in the amount of unrecognized tax benefits during the years ended December 31, 2018, 2017, and 2016:

	Year Ended December 31,
	2018			2017		2016
	(in thousands)
Beginning balance of unrecognized tax benefits	$	326		$	250	$	167
Additions for current year tax positions		142			65		75
Additions/reductions for prior year tax positions		(14	)		—		0
Ending balance (excluding interest and penalties)		454			315		242
Interest and penalties		15			11		8
Total	$	469		$	326	$	250

For the period ended December 31, 2018, 2017 and 2016, the Company has recorded income tax expense of $143,000, $76,000 and $83,000, respectively, related to uncertain tax positions. The Company’s policy is to recognize potential interest and penalties related to unrecognized tax benefits associated with uncertain tax positions, if any, in the income tax provision. At December 31, 2018, 2017 and 2016, the Company had accrued $15,000, $11,000 and $8,000 in interest and penalties related to uncertain tax positions.

The Company is subject to taxation in the United States and various states along with other foreign countries. Due to the presence of net operating loss carryforwards, all of the income tax years remain open for examination by the IRS and various state and foreign taxing authorities. However, the Company’s future results may include favorable or unfavorable adjustments to its estimates in the period the audits are resolved, which may impact the Company’s effective tax rate. The Company does not believe that it is reasonably possible that the total amount of unrecognized tax benefits will significantly increase or decrease in the next 12 months. The Company has not been notified that it is under audit by the IRS or state taxing authorities for any of the tax years currently open.

Deferred income taxes have not been provided for undistributed earnings of the Company’s consolidated foreign subsidiaries because of the Company’s intent to reinvest such earnings indefinitely in active foreign operations. At December 31, 2018, the Company had $0.6 million in unremitted earnings that were permanently reinvested related to its consolidated foreign subsidiaries.