Corporate tax is imposed in the United States at the federal, most state, and some local levels on the income of entities treated for tax purposes as corporations. Since January 1, 2018, the nominal federal corporate tax rate in the United States of America is a flat 21% due to the passage of the Tax Cuts and Jobs Act of 2017. State and local taxes and rules vary by jurisdiction, though many are based on federal concepts and definitions. Taxable income may differ from book income both as to timing of income and tax deductions and as to what is taxable. The corporate Alternative Minimum Tax was also eliminated by the 2017 reform, but some states have alternative taxes. Like individuals, corporations must file tax returns every year. They must make quarterly estimated tax payments. Groups of