As of and our deferred tax assets (“DTAs”) were approximately million and million, respectively. The components of our deferred tax assets are summarized as follows:

 

		As of December 31,
		201 9				201 8
Deferred tax assets:
Net operating loss carryforwards		$	31,966,658			$	29,597,313
R&D credit carryforwards			9,150,580				9,067,874
AMT credit carryforward			310,620				621,240
Stock compensation			382,016				375,731
Intangibles			610,783				550,797
Disallowed interest expense			857,648				878,929
Temporary differences			333,728				480,888
Deferred tax assets before valuation allowance			43,612,033				41,572,772
Valuation allowance			(43,301,413	)			(40,951,532	)
Net deferred tax assets		$	310,620			$	621,240

 

Current accounting standards require a valuation allowance against DTAs if, based on the weight of available evidence, it is more likely than that some or all of the DTAs be realized. Due to the uncertainty surrounding the realization of these DTAs in future tax returns, all of the DTAs have been fully offset by a valuation allowance at and except the alternative minimum tax (“AMT”) credit carryforward amount described below.

 

In assessing the realizability of DTAs, management considers whether it is more likely than that some portion or all of the DTAs will be realized. The ultimate realization of DTAs is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities (including the impact of available carryback and carryforward periods) and projected future taxable income in making this assessment. Based upon the level of historical taxable income and projections for future taxable income over the periods in which the DTAs are deductible, management believes it is more likely than that the Company will realize the benefits of these deductible differences or tax carryforwards as of except for the AMT credit carryforward.

 

The Tax Cuts and Jobs Act (the “Tax Act”) was signed into law on The Tax Act reduced the U.S. federal corporate tax rate from to effective Consequently, we recorded a decrease related to DTAs of million with a corresponding net adjustment to a valuation allowance of million for the year ended The Tax Act repeals the AMT for corporations, and permits any existing AMT credit carryforwards to be used to reduce the regular tax obligation in and Companies continue using AMT credits to offset any regular income tax liability in years through with of remaining AMT credits refunded in each of the and tax years, and all remaining credits refunded in tax year This results in full realization of an existing AMT credit carryforward irrespective of future taxable income. Accordingly, the Company recorded AMT credit carryforwards of and million as of and respectively, of which was included in prepaid and other current assets, and of which was included in other noncurrent assets as of and

 

As of and we had U.S. net operating loss carryforwards of approximately million and million, respectively. Of those amounts, million relates to stock-based compensation tax deductions in excess of book compensation expense (“APIC NOLs”) as of that will be credited to additional paid-in capital when such deductions reduce taxes payable as determined on a "with-and-without" basis. Accordingly, these APIC NOLs will reduce federal taxes payable if realized in future periods, but NOLs related to such benefits are included in the table above. As of we adopted ASU - and thereby eliminated all APIC NOLs with a full offset to a valuation allowance.

 

As of and we also had state net operating loss carryforwards of approximately million and million, respectively. The state net operating loss carryforwards will begin expiring in

 

At and we had U.S. R&D credit carryforwards of approximately million and million, respectively.

 

There were expirations of U.S. NOL carryforwards during or U.S. R&D credit carryforwards of and million expired during and respectively. 

 

The details of our U.S. net operating loss and federal R&D credit carryforward amounts and expiration dates are summarized as follows:

 

						As of December 31, 201 9
Generated		Expiration				U.S. Net Operating Loss Carryforwards				U.S. R&D Credit Carryforwards
2000		2020				$	—			$	71,713
2001		2021					—				39,128
2002		2022					—				5,350
2003		2023					—				2,905
2004		2024					—				22,861
2005		2025					—				218,332
2006		2026					—				365,541
2007		2027					—				342,898
2008		2028					—				531,539
2009		2029					—				596,843
2010		2030					—				1,094,449
2011		2031					—				1,950,744
2012		2032					18,850,484				468,008
2013		2033					37,450,522				681,772
2014		2034					34,088,874				816,116
2015		2035					25,073,846				492,732
2016		2036					15,581,209				262,257
2017		2037					—				387,892
2018		2038					—				197,547
2019		N/A					11,138,102				213,065
Total carryforwards						$	142,183,037			$	8,761,692

 

Under Sections and of the Internal Revenue Code (“IRC”) of as amended, the utilization of U.S. net operating loss and R&D tax credit carryforwards be limited under the change in stock ownership rules of the IRC.  The Company completed a Section analysis in and does believe a Section ownership change has occurred since then that would impact utilization of the Company’s net operating loss and R&D tax credit carryforwards.

 

Reconciliations between the statutory federal income tax rate and our effective tax rate for continuing operations are as follows:

 

		201 9								201 8
		Amount				%				Amount				%
Benefit at statutory rate		$	(2,299,122	)			(21.0	)%		$	(3,383,491	)			(21.0	)%
Adjustments to valuation allowance			2,355,947				21.5	%			2,458,580				15.3	%
Adjustments to R&D credit carryforwards			(82,706	)			(0.8	)%			975,840				6.1	%
Permanent items and other			26,588				0.3	%			(60,682	)			(0.3	)%
Provision (benefit) per financial statements		$	707							$	(9,753	)

 

See Note (p).