AMT Calculator Guide: What Is the Alternative Minimum Tax? (2026)

What Is the Alternative Minimum Tax?

The Alternative Minimum Tax is a parallel federal tax system that exists alongside the regular income tax. Every year, you effectively calculate your taxes twice — once under the standard rules and once under AMT rules — and you pay whichever result is higher.

Congress created the AMT in 1969 after a Treasury Department report revealed that 155 high-income taxpayers paid zero federal income tax that year by stacking deductions, credits, and preferences. The AMT was designed as a floor: a minimum amount that wealthy taxpayers must pay regardless of how many deductions they claim.

The AMT operates by computing Alternative Minimum Taxable Income (AMTI), which starts with your regular taxable income and then adds back certain deductions and “preference items” that the regular tax system allows but the AMT does not. You then subtract the AMT exemption and apply the AMT rates.

AMT Rates for 2025–2026

The AMT uses a two-bracket rate structure, which is simpler than the regular seven-bracket system:

This is your tentative minimum tax (TMT). If your TMT exceeds your regular tax liability, you owe AMT — specifically, the difference between the two.

AMT Exemptions for 2025–2026

The AMT exemption functions like a large standard deduction that reduces your AMTI before applying AMT rates. For most taxpayers, the exemption is large enough that AMT never applies. But for higher earners, the exemption phases out.

The phase-out reduces the exemption by $0.25 for every $1 of AMTI above the threshold. Once AMTI exceeds the phase-out completion amount, the exemption is fully eliminated and AMT applies to all AMTI.

Who Is Most Likely to Owe AMT?

According to IRS Statistics of Income data, the AMT has become increasingly concentrated among a narrow slice of taxpayers since TCJA 2017. Before the law passed, roughly 5 million taxpayers owed AMT annually. After TCJA, that number fell to approximately 200,000 — a 96% reduction.

The following groups face the highest AMT risk today:

1. ISO exercisers: Employees at pre-IPO startups or public companies who exercise incentive stock options face AMT on the spread between exercise price and FMV.
2. High earners with large preference items: Taxpayers with AMTI above the phase-out threshold who also have large depreciation deductions (e.g., oil and gas investments, real estate accelerated depreciation).
3. High-income single filers: The phase-out for single filers begins at $634,900 and completes at $987,300, concentrating AMT exposure in the upper-income range.
4. Taxpayers with large tax-exempt private activity bond interest: Interest on certain private activity bonds is excluded from regular income but added back for AMT.
5. Businesses with accelerated cost recovery: Certain depreciation methods (MACRS) that front-load deductions create an AMT preference item in earlier years.

5 AMT Triggers to Watch For

1. ISO stock option exercises: The spread on exercise (FMV minus exercise price) is the #1 AMT trigger for employees at venture-backed companies.
2. Accelerated depreciation deductions: Claiming bonus depreciation or Section 179 on business property can create an AMT preference item equal to the difference between MACRS depreciation and the AMT-allowed straight-line method.
3. Large state and local tax (SALT) deductions: Pre-TCJA, this was a primary trigger for residents of high-tax states. TCJA’s $10,000 SALT cap largely neutralized this — but if TCJA sunsets, SALT could become a major AMT trigger again.
4. Tax-exempt private activity bond interest: Interest from certain private activity bonds (e.g., housing bonds, student loan bonds) is tax-exempt under regular rules but is an AMT preference item.
5. Large miscellaneous itemized deductions: Before TCJA suspended them through 2025, deductions for unreimbursed employee expenses and investment advisory fees were added back for AMT purposes.

How ISO Stock Options Trigger AMT

Incentive stock options receive favorable regular-tax treatment: you owe no income tax when you exercise ISOs, only when you sell the shares (and then at long-term capital gains rates if held long enough). But the IRS has a different view for AMT purposes.

When you exercise ISOs, the “bargain element” — the spread between your exercise price and the stock’s fair market value — is added to your AMTI as a preference item. This can create a significant AMT liability even if you haven’t sold the stock and received no cash.

Here’s a simplified example:

If your regular tax on $180,000 W-2 income is less than $47,294, you owe the difference as AMT. The stock hasn’t been sold. No cash changed hands. But the tax bill is real. This is why employees at high-growth startups should model their AMT exposure before exercising ISOs — and why our AMT Calculator exists.

The AMT Credit After ISO Exercise

There is a silver lining. When you pay AMT due to ISO exercises, you accumulate an AMT credit (Minimum Tax Credit)tracked on IRS Form 8801. In future years when you no longer owe AMT — typically after you sell the shares and your regular tax rises — you can apply this credit against your regular tax. The credit effectively converts the AMT payment into a prepayment that you recover over time.

How to Calculate Whether You Owe AMT

The AMT calculation follows these steps:

1. Start with your regular taxable income.
2. Add back AMT preference items and adjustments (ISO spreads, accelerated depreciation, SALT if applicable, etc.).
3. This gives you your Alternative Minimum Taxable Income (AMTI).
4. Subtract the AMT exemption (which phases out above the threshold).
5. Apply 26% to the first $220,700, and 28% to amounts above that.
6. This is your Tentative Minimum Tax (TMT).
7. Subtract any applicable AMT foreign tax credit.
8. If TMT > regular tax, you owe AMT equal to the difference.

Use our AMT Calculatorto run through these steps automatically. The IRS also provides Form 6251 (Alternative Minimum Tax — Individuals) for the full official computation.

The TCJA Impact: AMT Before and After 2018

The Tax Cuts and Jobs Act of 2017 was the most significant AMT reform since the tax’s creation. Before TCJA, the AMT exemption was $55,400 for single filers and $86,200 for married filing jointly — low enough that millions of upper-middle-class families owed AMT, particularly in high-tax states like California and New York where SALT deductions were large.

The TCJA changes are currently set to sunset after 2025. If Congress does not extend them, exemptions revert to pre-2018 levels (adjusted for inflation), which would dramatically increase AMT exposure. Taxpayers who are currently not subject to AMT should model their liability under both scenarios.

Frequently Asked Questions

What is the Alternative Minimum Tax (AMT)?

The AMT is a parallel tax system that runs alongside the regular income tax. You calculate your taxes twice — once under the regular system and once under AMT rules — and pay whichever is higher. It was created in 1969 to ensure high-income taxpayers could not use deductions to eliminate their tax bill entirely. AMT uses two flat rates: 26% on the first $220,700 of AMTI above the exemption, and 28% on amounts above that.

Who pays the AMT?

After TCJA 2017 raised the exemptions and phase-out thresholds dramatically, roughly 200,000 taxpayers owe AMT annually — down from about 5 million before the law. Today, AMT most commonly hits people who exercise incentive stock options (ISOs), high earners with large accelerated depreciation deductions, and taxpayers in the income range where the AMT exemption phase-out applies. If TCJA sunsets, that number would rise sharply.

What is the AMT exemption for 2025 and 2026?

For 2025, the AMT exemption is $88,100 for single filers and $137,000 for married filing jointly. These phase out at $634,900 (single) and $1,269,800 (MFJ). The IRS adjusts these annually for inflation. The 2026 amounts will be confirmed in IRS Revenue Procedure 2025-40 or similar guidance. If TCJA sunsets, exemptions would revert to approximately $55,400 (single) and $86,200 (MFJ) in pre-2018 inflation-adjusted terms.

How do ISO stock options trigger AMT?

When you exercise ISOs, the spread between the exercise price and the stock’s fair market value on exercise date is not taxable for regular tax purposes — but it is added to your AMTI as a preference item. If that spread is large enough to push your AMTI above the exemption, you owe AMT even though you received no cash. This is a common and sometimes devastating surprise for employees at fast-growing startups who exercise large ISO grants.

Can you get a credit for AMT paid?

Yes. AMT paid due to timing differences (like ISO exercises) generates a Minimum Tax Credit (MTC) that carries forward indefinitely. In future years when your regular tax exceeds your tentative minimum tax, you can apply this credit to reduce your regular tax liability. It effectively makes the AMT a prepayment rather than a permanent cost. The credit is tracked on IRS Form 8801. AMT paid due to exclusion items (like certain bond interest) does not generate a credit.

What is Alternative Minimum Taxable Income (AMTI)?

AMTI is the income base for AMT calculations. Start with regular taxable income, then add back certain items: ISO exercise spreads, the SALT deduction (under pre-TCJA rules), accelerated depreciation on certain assets, certain tax-exempt bond interest, and other “preference items.” Subtract the AMT exemption (which phases out at higher incomes) and you have the AMTI that the 26%/28% AMT rates apply to.