Significant judgment is required in determining our provision for income taxes. The calculation of the provision for income taxes is subject to our interpretation of applicable business tax laws in the federal and state jurisdictions in which we file. In addition, our income tax returns are subject to periodic examination by the Internal Revenue Service, or IRS, and other taxing authorities.
In December 2014, we changed our tax method of accounting to permit the expensing of qualifying asset improvement costs that were previously being capitalized and depreciated for tax purposes. Our determination of what qualifies as a capital cost versus a repair expense tax deduction is subject to subsequent adjustment and may impact the income tax benefits that have been recognized. Although we believe our income tax estimates are appropriate, there is no assurance that the final determination of our income tax liability will not be materially different, either higher or lower, from what is reflected in our income tax provision. In the event we are assessed additional income taxes, our business, financial condition, and results of operations could be adversely affected.
In December 2017, the Tax Cuts and Jobs Act of 2017, or 2017 Tax Act, was signed into law. The 2017 Tax Act significantly changes how corporations are taxed. Significant judgments are required to be made in interpreting the provisions of the 2017 Tax Act and estimates may be required to comply with the provisions of the 2017 Tax Act. The U.S. Treasury Department, the IRS, and other standard-setting bodies could interpret or issue guidance on how provisions of the 2017 Tax Act will be applied or otherwise administered that is different from our interpretation. As additional regulatory guidance is issued by the applicable taxing authorities, as accounting treatment is clarified, as we perform additional analysis on the application of the law, and as we refine estimates in calculating the effect, our final analysis, which will be recorded in the period completed, may be different from our current provisional amounts, which could materially affect our tax obligations and effective tax rate.