what is the alternative minimum tax 
an alternative minimum tax amt places a floor on the percentage of taxes that a filer must pay to the government no matter how many deductions or credits the filer may claim the united states currently has an alternative minimum tax for taxpayers who earn above certain income thresholds the amt recalculates income tax after adding certain tax preference items back into adjusted gross income it uses a separate set of rules to calculate taxable income after allowed deductions preferential deductions are added back into the taxpayer s income to calculate their alternative minimum taxable income amti and then the amt exemption is subtracted to determine the final taxable figure 1