Alternative minimum tax

A tax intended to limit the extent to which higher-income people can reduce their tax liability (the amount they owe) through the use of preferences in the tax code. 
Taxpayers subject to the Alternative minimum tax(AMT) are required to recalculate their tax liability on the basis of a more limited set of exemptions, deductions, and tax credits than would normally apply. The amount by which a taxpayer’s AMT calculation exceeds his or her regular tax calculation is that person’s AMT liability.