When looking over your tax return, do you notice an amount on line 45? That amount is because you are subject to the alternative minimum tax. The Alternative Minimum Tax or AMT is an income tax that does not allow some of the tax preferences and deductions that regular tax computation allows. Basically, a punitive tax. When an AMT computation results in a higher tax, the higher tax applies. The additional tax from the Alternative Minimum Tax is added on line 45 of your return.