The Company had no income tax expense for the years ended December 31, 2020 and 2019. Due to uncertainties surrounding the realization of its deferred income tax assets in future periods, the Company has recorded a 100% valuation allowance against its net deferred income tax assets. If it is determined in the future that it is more likely than not that any deferred income tax assets are realizable, the valuation allowance will be reduced by the estimated net realizable amounts. For the years ended December 31, 2020 and 2019, the valuation allowance increased by $0.7 million and $1.3 million, respectively, based on changes in deferred tax assets and liabilities.

The tax effect of temporary differences and net operating losses that give rise to components of deferred income tax assets and liabilities consist of the following:

At December 31, 2020, the Company had cumulative federal and state net operating losses of approximately $90 million and $35 million, respectively, available to reduce future taxable income, if any. The federal net operating loss carryforward begins expiring in 2021, and the state net operating loss carryforward begins expiring in 2028. It is possible that the Company will not generate taxable income in time to use these net operating loss carryforwards before their expiration. In addition, under Section 382 of the Internal Revenue Code of 1986 (the “Code”), as amended, if a corporation undergoes an “ownership change” (as defined in the Code), the corporation’s ability to use its pre-change tax attributes to offset its post-change income may be limited. In general, an “ownership change” occurs if there is a cumulative change in a “loss corporation’s” (as defined in the Code) ownership by 5% shareholders that exceeds 50 percentage points over a rolling three-year period. The Company has not determined whether such an ownership change has occurred. However, given the equity transactions in which the Company has engaged, the Company believes that the use of the net operating losses shown as deferred tax assets will be significantly limited.

Management has evaluated the effect of guidance provided by GAAP regarding accounting for uncertainty in income taxes and determined the Company has no uncertain tax positions that could have a significant impact on its consolidated financial statements. The Company’s federal income tax return for 2017 and subsequent years remain open for examination.