United States federal income tax incorporates an alternative minimum tax. This tax is computed at a lower tax rate (20% for corporations), and imposed based on a modified version of taxable income. Modifications include longer depreciation lives assets under MACRS, adjustments related to costs of developing natural resources, and an addback of certain tax exempt interest.[52]

Corporations may also be subject to additional taxes in certain circumstances. These include taxes on excess accumulated undistributed earnings and personal holding companies[53] and restrictions on graduated rates for personal service corporations.[54]

Some states, such as New Jersey, impose alternative taxes based on measures other than taxable income. Among such measures are gross income, pipeline revenues, gross receipts, and various asset or capital measures. In addition, some states impose a tax on capital of corporations or on shares issued and outstanding. The U. S. state of Michigan previously taxed businesses on an alternative base that did not allow compensation of employees as a tax deduction and allowed full deduction of the cost of production assets upon acquisition.

http://en.wikipedia.org/wiki/Corporate_tax_in_the_United_States

Taxes are never simple regarding corporations.