What is the Alternative Minimum Tax (AMT)
The Alternative Minimum Tax (AMT) is a parallel tax calculation that applies when it would result in a higher bill than the regular income tax — it disallows certain deductions to ensure high earners pay at least a minimum amount of tax.
The Alternative Minimum Tax (AMT) is a separate, parallel income tax calculation that applies to taxpayers above certain income levels. When the AMT produces a higher tax liability than the regular income tax calculation, the taxpayer pays the higher amount. The AMT system was created in 1969 after Congress discovered that 155 high-income Americans had paid zero federal income tax — the AMT was designed to ensure that wealthy taxpayers who benefit heavily from deductions and preferences still pay a baseline level of tax.
After 2017 tax law changes dramatically increased the AMT exemptions, far fewer middle-income taxpayers are subject to the AMT today. But it still affects many high earners and those with specific types of large deductions.
How AMT Is Calculated
The AMT calculation runs parallel to your regular income tax:
- Start with regular taxable income
- Add back "preference items" — specific deductions that are disallowed for AMT purposes (see below)
- Subtract the AMT exemption (based on income and filing status)
- Apply the AMT rate (26% on the first ~$220,700; 28% above that for 2025)
- If the AMT result exceeds your regular tax, you pay the difference as "AMT" on top of regular tax
2025 AMT Exemptions and Phase-Outs
| Filing Status | AMT Exemption | Phase-Out Starts |
|---|---|---|
| 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 $0.25 per dollar of AMTI above the threshold—effectively increasing the AMT rate by 7 percentage points in the phase-out range.
Items That Trigger AMT (Preference Items)
Certain deductions and tax benefits that reduce regular income tax are disallowed or limited under AMT:
| Item | AMT Treatment |
|---|---|
| State and local tax (SALT) deduction | Completely disallowed |
| Standard deduction | Disallowed (AMT requires adding back) |
| Miscellaneous itemized deductions | Disallowed |
| Depreciation (for real property) | Accelerated depreciation is added back |
| Incentive stock options (ISOs) | Spread on exercise is an AMT preference item |
| Tax-exempt interest from private activity bonds | Added back |
Common AMT Triggers in Practice
The most common situations that generate significant AMT liability:
- High-income earners in states with high state income taxes, since SALT is disallowed for AMT
- Incentive stock options: Exercising ISOs generates no regular tax at exercise, but the "spread" (difference between fair market value and exercise price) is added back for AMT purposes — this can create very large AMT bills for employees at pre-IPO companies
- Large depreciation deductions: Especially for real estate professionals and businesses
- Long-term capital gains: These don't directly trigger AMT but can phase out the AMT exemption
AMT Credit (Form 8801)
If you paid AMT in a prior year due to "deferral preferences" (items that create a temporary timing difference, like ISO exercises), you may be eligible for a minimum tax credit in future years when your regular tax exceeds your tentative minimum tax. This credit allows some of the AMT paid to be recovered over time. Track this credit using Form 8801.
How to Know If You Owe AMT
Tax software calculates AMT automatically — you'll see it if it applies. If you're doing manual calculations, complete IRS Form 6251 (Alternative Minimum Tax — Individuals) to determine your AMT liability. Major warning signs:
- AGI above $150,000–$200,000+
- Large SALT deductions
- Significant ISO exercises
- Large passive activity losses being deducted