Alternative Minimum Tax (AMT) Definition, How It Works

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.

How the Alternative Minimum Tax Works

The difference between a taxpayer's alternative minimum taxable income and his AMT exemption is taxed using the relevant rate schedule. This yields the tentative minimum tax (TMT).

If the tentative minimum tax is higher than the taxpayer's regular tax liability for the year, then they pay the regular tax and the amount by which the tentative minimum tax exceeds the regular tax. In other words, the taxpayer pays the full tentative minimum tax.

There are two alternative minimum tax rates, 26% and 28%. For 2022, the 28% rate applies to the excess alternative minimum taxable income of $206,100 or more for all taxpayers ($103,050 for married couples filing separate returns). For 2023, the 28% rate applies to the excess alternative minimum taxable income of $220,700 or more for all taxpayers ($110,350 for married couples filing separate returns). The 26% rate applies to incomes up to those levels.

A taxpayer who has a high income and uses large tax breaks may owe a smaller percentage under the standard rules. If so, the taxpayer is obliged to recalculate the taxes owed under the alternative minimum tax system, which eliminates some of those tax breaks.

The taxpayer will owe whichever amount is higher.

AMT Exemption Amounts

For tax year 2022, the AMT exemption for single filers is $75,900. For married joint filers, the figure is $118,100. For tax year 2023, the figures are $81,300 for single filers and $126,500 for married joint filers.

Taxpayers have to complete Form 6251 to see whether they might owe AMT. First, they subtract the exemption amount from their income. If their AMT is less than the exemption, they do not have to pay AMT.

It's important to note, though, that taxpayers with AMTI over a certain threshold do not qualify for the AMT exemption. For tax year 2022, the phase-out begins at $539,900 for single filers and $1,079,800 for couples filing jointly. For tax year 2023, the phase-out begins at $578,150 for single filers and $1,156,300.

Purpose of AMT

AMT is designed to prevent taxpayers from escaping their fair share of tax liability through tax breaks. However, in the past, the structure was not indexed to inflation or tax cuts. This can cause bracket creep, a condition in which middle-income taxpayers could be subject to this tax instead of just the wealthy taxpayers for whom AMT was invented. In 2012, however, Congress passed a law indexing the AMT exemption amount to inflation.

Calculating AMT

To determine if they owe AMT, individuals can use tax software that automatically does the calculation, or they can fill out IRS Form 6251. This form takes medical expenses, home mortgage interest, and several other miscellaneous deductions into account to help tax filers determine if their deductions are beyond an overall limit set by the IRS.

The form also requests information on certain types of income such as tax refunds, investment interest, and interest from private activity bonds, as well as numbers corresponding with capital gains or losses related to the disposition of property.

The IRS has specific formulas in place to determine which portion of this income and deductions the tax filers need to note on Form 6251. It uses another set of formulas to determine how these numbers lead to AMTI.

The Bottom Line

The Alternative Minimum Tax is an additional or parallel tax system in the U.S. that is designed to ensure that high-income individuals pay their fair share of taxes. Prior to the AMT, certain taxpayers paid little in the way of taxes, due to preferential treatment of certain income and expenses, or tax breaks.