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## NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued) 

The tax effects of significant temporary differences representing the net deferred tax asset and liability at December 31, 2012 and 2013 were as follows: 

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At December 31, 2013, Comstock had the following carryforwards available to reduce future income taxes: 

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Utilization of $34.7 million of the U.S. federal net operating loss carryforwards is limited to approximately $1.1 million per year pursuant to a prior change of control of an acquired company, and a valuation allowance of $23.0 million, with a tax effect of $8.0 million, has been established for the estimated U.S. federal net operating loss carryforwards that will not be utilized. Realization of the remaining U.S. federal net operating loss carryforwards requires Comstock to generate taxable income within the carryforward period. A valuation allowance of $528.1 million, with a tax effect of $27.5 million, has been established against the Louisiana state net operating loss carryforwards due to the uncertainty of generating taxable income in the state of Louisiana prior to the expiration of the carryforward period. 

The Company’s federal income tax returns for the years subsequent to December 31, 2009 remain subject to examination. The Company’s income tax returns in major state income tax jurisdictions remain subject to examination for various periods subsequent to December 31, 2008. State tax returns in two state jurisdictions are currently under review. The Company currently believes that resolution of these matters will not have a material impact on its financial statements. The Company currently believes 

