The tax law gives preferential treatment to some kinds of income and allows special deductions and credits for some kinds of expenses. Taxpayers who benefit from these provisions of the law may have to pay an additional tax called the alternative minimum tax. It is a separate tax computation that, in effect, eliminates many deductions and credits and creates a tax liability for an individual who would otherwise pay little or no tax.
The exemption amounts for figuring the AMT depend on your filing status. You may have to pay AMT if your taxable income for regular tax purposes, combined with certain adjustment and tax preference items, is more than the exemption amounts below:
$109,400 if married filing jointly or qualifying widow(er);
$70,300 if you are single or head of household, or
$54,700 if you are married filing a separate return.
Also, the amount used to determine the phaseout of your exemption has increased to $500,000 ($1,000,000 if married filing jointly).
For more information on this tax see the instructions for form 6251.