A reconciliation of the provision for income taxes to the amount computed by applying the statutory income tax rate of 21% to the net loss is summarized for the years ended December 31, 2021 and 2022 is as follows:

For the years ended December 31, 2021 and 2022, the Company did not record a deferred income tax expense or benefit. Income tax expense has been nominal for the years ended December 31, 2021 and 2022.

Deferred tax assets and liabilities are recognized for the expected tax consequences attributable to the differences between financial reporting and the tax basis of existing assets and liabilities and operating loss carryforward, and they are measured using enacted tax rates expected to be in effect when differences are expected to reverse. A valuation allowance is recorded for loss carryforwards and other deferred tax assets where it is more likely than not that such loss carryforward and deferred tax asset will not be realized. Significant components of the Company’s deferred tax assets at December 31, 2021 and 2022 are shown below (in thousands):

The valuation allowance increased by $4.4 million during the year ended December 31, 2022. The Company has concluded, based upon ASC 740, that it is more likely than not the Company will not realize any benefit from the deferred tax assets related to certain Federal and state’s net operating loss and credit carryforwards. Accordingly, the Company has established a full valuation allowance against its Federal and state deferred tax assets.

As of December 31, 2022, the Company had available Federal and California net operating loss carryforwards of approximately $15.4 million and $13.1 million to reduce future taxable income, if any. Federal net operating losses generated prior to 2018 and all state net operating losses generated expire in varying amounts beginning in 2037. These net operating losses, generated after 2017, do not expire and will be able to offset 80% of taxable income generated in the future.

As of December 31, 2022, the Company had research and development credit carryforwards of approximately $444,000 and $245,000 available to reduce future taxable income, if any, for federal and state income tax purposes, respectively. These credits have been provided a full reserve under ASC 740-10. The federal credit carryforwards begin to expire in 2037, and the state credit carryforwards can be carried forward indefinitely.

Utilization of net operating losses and tax credits may be subject to an annual limitation due to ownership change limitations provided in the Internal Revenue Code of 1986, as amended (the “Code”), and similar state provisions. The effect of an ownership change would be the imposition of annual limitation on the use of net operating loss (“NOL”) carryforwards attributable to periods before the change in ownership. An assessment of such ownership changes under Section 382 of the Code was not completed through December 31, 2022 and, as such the Company is not able to determine the impact on the NOLs and tax credit carryforwards, if any, as of the date of the financial statements. To the extent that an assessment is completed in the future, the Company’s ability to utilize tax attributes could be restricted on a year-by-year basis and certain attributes could expire before they are utilized.

On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) was enacted in response to the COVID-19 pandemic. The CARES Act, among other things, permits NOL carryovers and carrybacks to offset 100% of taxable income for taxable years beginning before 2021. In addition, the CARES Act allows NOLs incurred in 2018, 2019, and 2020 to be carried back to each of the five preceding taxable years to generate a refund of previously paid income taxes. Due to the Company’s history of NOLs, the CARES Act did not have a material impact on the Company’s financial statements.

The Company applies the guidance under ASC 740, subtopic 10-50-15, Unrecognized Tax Benefit Related Disclosures (formerly FASB Interpretation 48, Accounting for Uncertainty in Income Taxes). For benefits to be realized, a tax position must be more likely than not to be sustained upon examination by tax authorities. The amount recognized is measured as the largest amount of benefit that is greater than 50% likely of being realized upon settlement. This interpretation also provides guidance on measurement, de-recognition, classification, interest and penalties.

The Tax Cuts and Jobs Act (“TCJA”) included a change in the treatment of research and development (“R&D”) expenditures for tax purposes under Section 174. Effective for tax years beginning after December 31, 2021, specified R&D expenditures must undergo a 5-year amortization period for domestic spend and a 15-year amortization period for foreign spend. Prior to the effective date (2021 tax year and prior), taxpayers were able to immediately expense R&D costs under Section 174(a) or had the option to capitalize and amortize R&D expenditures over a 5-year recovery period under Section 174(b). The Company has evaluated the current legislation at this time and prepared the provision by following the treatment of R&D expenditures for tax purposes under Section 174.

The following table summarizes the changes to the Company’s gross unrecognized tax benefits for the years ended December 31, 2021 and 2022 (in thousands):

As of December 31, 2021 and 2022, the total unrecognized tax benefit was approximately $101,000 and $690,000, respectively. The Company does not expect any material changes to the estimated amount of liability associated with its uncertain tax positions within the next 12 months. The Company’s policy is to recognize interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2022, the Company had no accrued interest and penalties related to uncertain tax positions.

The Company files U.S. and state income tax returns with varying statutes of limitations. Tax years 2018 and forward remain open to examination due to the carryover of NOL carryforwards. There are no ongoing examinations by taxing authorities at this time.