
	Year Ended December 31,
	2020		2019		2018
	(Thousands of Dollars)
Current:
U.S.	$	36	$	3,741	$	4,515
Foreign	2,415		1,489		4,658
Foreign withholding tax	—		101		192
Total current	2,451		5,331		9,365

Deferred:
U.S.	300		(490)		1,403
Foreign	(621)		(168)		394
Foreign withholding tax	533		182		246
Total deferred	212		(476)		2,043

Less: amounts reported in discontinued operations	—		101		1,251

Income tax expense	$	2,663	$	4,754	$	10,157

The difference between income tax expense recorded in our consolidated statements of (loss) income and income taxes computed by applying the applicable statutory federal income tax rate to income before income tax expense is due to the fact that the majority of our income is not subject to federal income tax due to our status as a limited partnership. We record a tax provision related to the amount of undistributed earnings of our foreign subsidiaries expected to be repatriated.


	December 31,
	2020		2019
	(Thousands of Dollars)
Deferred income tax assets:
Net operating losses	$	18,459	$	26,081
Employee benefits	134		372
Environmental and legal reserves	105		267

Capital loss	10,813		3,870
Other	834		693
Total deferred income tax assets	30,345		31,283
Less: Valuation allowance	(28,211)		(17,743)
Net deferred income tax assets	2,134		13,540

Deferred income tax liabilities:
Property, plant and equipment	(13,772)		(25,169)
Foreign withholding tax	(1,002)		(433)
Other	(371)		(365)
Total deferred income tax liabilities	(15,145)		(25,967)

Net deferred income tax liability	$	(13,011)	$	(12,427)

As of December 31, 2020, our U.S. and foreign corporate operations have net operating loss carryforwards for tax purposes totaling $58.0 million and $21.0 million, respectively, which are subject to various limitations on use and expire in years 2025 through 2037 for U.S. losses and in years 2019 through 2029 for foreign losses. However, U.S. losses generated after December 31, 2017, totaling $4.9 million, can be carried forward indefinitely. As of December 31, 2020, our U.S. corporate operations have a capital loss carryforward for tax purposes totaling $51.5 million, of which $17.7 million is subject to limitations on use and expires in 2024, and the remaining amount expires in 2025.

As of December 31, 2020 and 2019, we have a valuation allowance of $28.2 million and $17.7 million, respectively, related to our deferred tax assets on net operating losses and capital losses. We estimate the amount of valuation allowance based upon our expectations of taxable income in the various jurisdictions in which we operate and the period over which we can utilize those future deductions. The valuation allowance reflects uncertainties related to our ability to utilize certain net operating loss carryforwards before they expire. In 2020, there was a $10.0 million increase in the valuation allowance for the U.S. net operating loss and a $0.5 million increase in the foreign net operating loss valuation allowance due to the Texas City Sale and changes in our estimates of the amount of loss carryforwards that will be realized, based upon future taxable income.

The realization of net deferred income tax assets recorded as of December 31, 2020 is dependent upon our ability to generate future taxable income in the United States. We believe it is more likely than not that the net deferred income tax assets as of December 31, 2020 will be realized, based on expected future taxable income.