The Alternative Minimum Tax is a parallel tax system designed to ensure that high-income taxpayers cannot use deductions and credits to reduce their regular tax bill to near zero. If your AMT liability exceeds your regular income tax, you pay the difference as AMT. Here is how it works and who needs to worry about it in 2025.
Why the AMT Exists
Congress created the AMT in 1969 after learning that 155 high-income Americans paid zero federal income tax by stacking deductions. The AMT requires taxpayers to recalculate their taxes under a separate set of rules that disallow many deductions and credits allowed under the regular system.
How AMT Is Calculated
AMT uses its own income measure called Alternative Minimum Taxable Income (AMTI), calculated by starting with your regular taxable income and adding back certain “preference items” and adjustments, including:
- State and local tax deductions (SALT) — one of the biggest add-backs
- Certain business deductions that are accelerated under regular tax rules
- Exercise of incentive stock options (ISOs) — the spread on ISO exercise is AMTI income
- Certain tax-exempt interest from private activity bonds
After calculating AMTI, you subtract the AMT exemption (see below), then apply the AMT rate.
2025 AMT Tax Rates
The AMT has two rates:
- 26% on AMTI up to $232,600
- 28% on AMTI above $232,600
These rates are lower than the top ordinary income rates, but the AMT base is much broader because many deductions are disallowed.
2025 AMT Exemptions
The AMT exemption is a significant amount you can subtract from AMTI before calculating the tax:
| Filing Status | Exemption | Phase-Out Begins |
|---|---|---|
| Single | $88,100 | $626,350 |
| Married Filing Jointly | $137,000 | $1,252,700 |
| Married Filing Separately | $68,500 | $626,350 |
The exemption phases out at 25 cents for every dollar of AMTI above the threshold. Once AMTI exceeds the threshold by four times the exemption amount, the exemption is fully phased out.
Who Actually Pays AMT in 2025
Thanks to the Tax Cuts and Jobs Act of 2017, which dramatically increased exemptions, far fewer taxpayers owe AMT than in prior years. Today, AMT primarily affects:
- High earners with significant SALT deductions — particularly those in high-tax states like California and New York
- Taxpayers who exercised incentive stock options (ISOs) and did not sell the shares in the same year
- Individuals with very large capital gains or certain tax-exempt bond income
- Households with income between roughly $500,000 and $2 million — the phase-out range where exemptions disappear and the regular tax structure sometimes provides too many benefits
Middle-income taxpayers with straightforward W-2 income are rarely affected by AMT in 2025.
The AMT Credit
If you pay AMT in a given year, you may be able to carry forward an AMT credit to offset regular tax in future years when your regular tax exceeds AMT. This is particularly relevant for ISO holders who triggered AMT and later sell the shares.
ISO Exercise and AMT: A Common Trap
Exercising incentive stock options does not trigger regular income tax — but it does trigger AMT. The spread between the exercise price and fair market value of the stock is added to AMTI. If you exercise a large number of ISOs and hold the shares (to qualify for long-term capital gains treatment when you sell), you could owe significant AMT even though you have received no cash.
The classic trap: exercise ISOs in a year when the stock is at a high price, owe substantial AMT, then see the stock decline before you sell. You owe tax on phantom income, and the stock is now worth less than the tax bill.
If you are planning a significant ISO exercise, model the AMT impact carefully before the end of the year.
Strategies to Manage AMT
- Exercise ISOs in years when your AMTI is lower — spread exercises across multiple years to stay below the exemption phase-out
- Avoid triggering large SALT add-backs — state tax planning is less effective against AMT
- Consider the timing of deductions — bunching itemized deductions in one year may increase regular tax deductions but also increase AMT exposure in that year
- Work with a tax advisor for ISO planning — the interaction between regular tax and AMT on stock options is complex enough that professional guidance usually pays for itself
Bottom Line
Most taxpayers do not pay AMT in 2025 due to the substantially higher exemptions put in place after 2017. However, if you are a high earner with significant SALT deductions, live in a high-tax state, or exercise incentive stock options, AMT deserves a careful look. Running a quick AMT calculation as part of your year-end tax planning can help you avoid surprises in April.