Taxes | September 8, 2021

Beware of These AMT Triggers

Nobody enjoys paying taxes, but if you had to pick one tax that is almost universally disliked, it’s the alternative minimum tax (AMT). As with any controversial topic, there are many opinions about the AMT—and, unfortunately, a lot of misinformation.

What is the AMT?

The easiest way to understand the AMT is to envision it as a tax floor. Once your tax rate drops to that floor, the AMT won’t allow it to go any lower.

Originally, the AMT was intended to crack down on wealthy people who weren’t paying any income taxes. Gradually, as inflation caused incomes to rise, the middle class started to get hit with this tax.

When Congress passed the Tax Cuts and Jobs Act (TCJA) in December 2017, the AMT rules significantly changed. However, the changes are temporary and apply only to tax years 2018 to 2025 unless Congress extends them or makes them permanent.

How does the AMT work?

Let’s look at a simple example.

In general, start by calculating your ordinary taxable income using IRS Form 1040. Then, on IRS Form 6251, add back some types of income and drop certain deductions.

Be sure to include income that might be tax-free under the normal income tax system but not under the AMT. One example is interest from private-activity municipal bonds, which fund private company projects that benefit the public (like airports).

Next, remove certain tax breaks, such as your deductions for state, local, and property taxes.

Then, subtract your AMT exemption (if eligible), which for the 2021 tax year is $73,600 for individuals, $57,300 for married couples filing separately, and $114,600 for married couples filing jointly or qualifying widow(er).

Finally, compute the AMT on what’s left, compare that amount with what you would owe under the regular system, and pay the higher of the two.

What are the chances the AMT will affect you?

Prior to the passage of the TCJA (tax years 2017 or earlier), if your household income was over $200,000 per year, you had about a 56% chance that the AMT would show up on your tax return.¹ With those odds, many people were rightfully concerned about the AMT affecting them.

Today, your odds of encountering the AMT are much lower, primarily because of two significant changes within the TCJA: an increase in the AMT exemptions and an increase in the phase-out thresholds. The chart below compares the prior AMT exemption to the current exemption under the TCJA.

AMT exemptions

Type of taxpayer

2017 exemption

2021 TCJA exemption

Change in exemption

Single filer




Married filing jointly or qualifying widow(er)




Married filing separately




Source: IRS

Along with the increased exemption, the point at which the exemption begins to phase out has been significantly increased.

AMT exemption phase-out thresholds

Type of taxpayer

2017 phase-out threshold

2021 TCJA phase-out threshold

Change in phase-out

Single filer




Married filing jointly or qualifying widow(er)




Married filing separately




Source: IRS

Once your income for the AMT hits the phase-out threshold, your AMT exemption begins to phase out at 25 cents for every dollar over the threshold. In the past, the phase-out level was quite low, and many households that wouldn’t consider themselves to be wealthy were getting affected by the AMT.

TCJA also made changes to itemized deductions, such as reducing the deduction for the taxes you paid and removing the deduction for various miscellaneous expenses. Combined, these changes should result in the vast majority of households not having to be concerned with the AMT affecting them. That said, the AMT could still kick in if the triggers listed below apply to you.

What triggers the AMT for tax years 2018 to 2025?

These are some of the most likely situations:

  • Having a high household income. If your household income is over the phase-out thresholds ($1,047,200 for married filing jointly and $523,600 for everyone else), and you have a significant amount of itemized deductions, the AMT could still affect you.
  • Realizing a large capital gain. Long-term gains (e.g., profits from selling a home or other investments) are taxed at the same rate under both systems, but capital gains could put you over the AMT exemption threshold. That could cause the AMT to kick in, which means you may not be able to deduct state income taxes you paid.
  • Exercising stock options. Normally, exercising qualified employee stock options (also called incentive stock options or ISOs) to buy stock at a discounted price isn't a taxable event until you sell the shares for a profit. The AMT, however, creates a paper profit that’s taxable even though you won't receive the actual profit until you sell the shares.

If you’re close to the AMT thresholds, you can use IRS Form 6251 to see if you’re at risk. You can also run your own projections using tax preparation software or hire a tax professional to calculate it for you.

Depending on your income and deductions, you could find yourself affected by the AMT in one tax year but not the next. If you’re close to the AMT threshold, doing a multiyear projection is good practice to see which tax years pose the most risk for you and how you might mitigate that risk. For example, you could accelerate or delay certain transactions, such as selling an asset with a large gain, to minimize triggering the AMT.

Getting hit with the AMT is unfortunate, but it’s not a reason to change your life goals. The AMT is just something to be aware of during your financial planning process—it shouldn’t keep you up at night.

A quick history of the AMT

Back in 1969, marginal tax rates ran as high as 70%, and the tax code was full of loopholes. Congress became aware that some households with incomes over $200,000 had managed to avoid paying any federal income tax.

Congress and the public were outraged, so the AMT was designed to remove certain tax breaks from the wealthiest filers and force them to pay at least a minimum amount of tax.

Unfortunately, lawmakers didn't consider the effects of inflation on the original tax law. Over the decades, as wages increased to keep up with inflation, the AMT began to affect more and more households.

The TCJA has since fixed these flaws; however, these changes are temporary and only affect tax years 2018 to 2025. After 2025, the AMT could once again become a problem for middle-class taxpayers.

¹Source: Schwab Center for Financial Research, based on information in the IRS publication “Statistics of Income–2014 Individual Income Tax Returns Complete Report” (Publication 1304), Table 1.4.

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