On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act makes broad and complex changes to the U.S. tax code that will affect our fiscal year ended December 29, 2017, including, but not limited to, (1) reducing the U.S. federal corporate tax rate to 21%; (2) eliminating the corporate alternative minimum tax (AMT) and changing how existing AMT credits can be realized; (3) creating the base erosion anti-abuse tax (BEAT), a new minimum tax; (4) creating a new limitation on deductible interest expense; (5) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017; (6) bonus depreciation that will allow for full expensing of qualified property; and (7) imposing limitations on the deductibility of certain executive compensation. In connection with our initial analysis of the impact of the Tax Act, we recorded an additional tax expense of approximately $349,000 in the fourth quarter of 2017. This expense is primarily due to remeasurement of our net deferred tax assets at the enacted rate of 21% compared to the previous rate of 34%.

The provision for deferred income taxes is comprised of the following:

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred taxes are as follows:

Our charitable contribution carryover will expire in the years 2017 through 2018.

Management estimates that our combined federal and state tax rates was approximately 25.4% for 2017, net of federal benefit on state income taxes. The items accounting for the difference between income taxes computed at the statutory federal income tax rate and the income taxes reported on the statements of income are as follows:

We have analyzed our filing positions in all jurisdictions where we are required to file income tax returns and found no positions that would require a liability for unrecognized income tax benefits to be recognized. We include interest and penalties as interest expense on the consolidated financial statements.