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AMT Calculator (2026)

Alternative Minimum Tax, and the exemption that erodes above $500K

Data verified: Aug 2026 · Source: IRS Rev. Proc. 2025-32

An AMT calculator for 2026, including the exemption phaseout that OBBBA pulled back to 2018 thresholds — so far more households now lose it.

Your details
The standard deduction is not allowed against AMT, so it is added back into AMTI.
Additional AMT owed
—
Alternative minimum taxable income —
Base exemption (—) —
Exemption lost to phaseout —
Exemption you keep —
AMT base —
Tentative minimum tax —
Regular tax —
AMT owed —
AMT owed vs. taxable income
Taxable income

How this is calculated

The Alternative Minimum Tax is a parallel tax system. You compute your liability twice — once under the ordinary rules and once under the AMT rules, which disallow several deductions and add back certain preference items — and you pay whichever is higher. The AMT figure quoted is the excess of the tentative minimum tax over the regular tax.

The 2026 change that matters is the exemption phaseout threshold. OBBBA pulled it back from the 2025 levels of $625,350 single and $1,252,700 joint down to $500,000 and $1,000,000. Combined with a 25% phaseout rate, that puts far more households into the range where the exemption erodes.

Formula
AMTI = taxable income + preference add-backs (+ standard deduction if taken) exemption = max(0, base − 0.25 × max(0, AMTI − phaseout start)) amtBase = max(0, AMTI − exemption) TMT = amtBase ≤ $244,500 ? 0.26 × amtBase : 0.26 × $244,500 + 0.28 × (amtBase − $244,500) AMT owed = max(0, TMT − regular tax)
2026 constants: exemption $90,100 single and $140,200 joint; phaseout starts at $500,000 and $1,000,000 respectively at 25 cents per dollar; the 28% rate applies above $244,500 of AMT base, or $122,250 for married filing separately.

Worked example

Married filing jointly with AMTI of $1,100,000 and a regular tax liability of $250,000.

Exemption before phaseout$140,200
Phaseout: 25% × ($1,100,000 − $1,000,000)−$25,000
Exemption retained$115,200
AMT base$984,800
Tentative minimum tax$270,854
Less regular tax−$250,000
AMT owed$20,854

The classic triggers

AMT rarely arrives out of nowhere. These are the usual causes.

  • Exercising incentive stock options and holding the shares — the bargain element is an AMT preference even though it is not ordinary income.
  • Large state and local tax deductions, which AMT disallows entirely.
  • Private activity municipal bond interest, which is tax-exempt for regular tax but not for AMT.
  • A very large long-term capital gain, which does not itself get taxed at AMT rates but pushes AMTI up and phases out the exemption.

Capital gains inside AMT

Long-term capital gains and qualified dividends keep their preferential rates under AMT — they are not converted to 26 or 28% income. But they do count in AMTI, so a large gain can strip your exemption and create AMT on your other income. This calculator treats the whole AMT base at the 26/28% rates; if a large share of your income is long-term gains, model that layer separately for an accurate figure.

The AMT credit

AMT paid because of a timing preference — most commonly an ISO exercise — generally generates a minimum tax credit you can use against regular tax in later years. AMT caused by a permanent difference, such as disallowed SALT, does not.

Frequently asked questions

What changed for AMT in 2026?
The exemption phaseout thresholds dropped sharply to $500,000 for single filers and $1,000,000 for joint filers under OBBBA, down from $625,350 and $1,252,700 in 2025. The exemption amounts themselves rose slightly, to $90,100 and $140,200, but the much lower phaseout start means far more households now sit inside the range where the exemption erodes.
Why is the effective rate above 28%?
Inside the phaseout, each additional dollar of alternative minimum taxable income does two things: it gets taxed at 28%, and it removes twenty-five cents of exemption, which is then itself taxed. The combined effect is an effective marginal rate of roughly 35% on income in that band, well above the headline AMT rate anyone would expect.
Do incentive stock options really trigger this?
They are the single most common cause. Exercising an ISO and holding the shares creates a bargain element that is completely invisible for regular tax but fully counted as an AMT preference. The result is a real cash tax bill on a paper gain you have not realized, which is why people exercise and then discover they owe money they do not have.
Is AMT on top of my regular tax?
No. You compute your liability twice, under the ordinary rules and under the AMT rules, and you pay whichever is higher. The figure shown here is the difference between the two, which is the additional amount you would owe. If your tentative minimum tax comes out below your regular tax, you owe no AMT at all that year.
Can I get AMT back later?
Sometimes. AMT that arises from a timing difference, most commonly an ISO exercise, generally generates a minimum tax credit you can use against regular tax in future years, so the money comes back eventually. AMT caused by a permanent difference, such as disallowed state and local tax, does not generate a credit and is simply gone.
Does the standard deduction count?
It is not allowed against AMT. If you took the standard deduction for regular tax purposes, it has to be added back when computing your alternative minimum taxable income, which is what the checkbox on this calculator does. The same applies to state and local taxes, which AMT disallows entirely regardless of whether you itemized.

Related calculators

SALT Deduction Calculator How much of your state and local tax payment survives the 30% phaseout. Roth Conversion Calculator Conversion room to the top of your bracket, with IRMAA and ACA warnings. Tips, Overtime, Car Loan & Senior Deductions Stack all four OBBBA deductions with their separate MAGI phaseouts. Estate & Inheritance Tax by State Federal plus the 12 estate-tax states, 5 inheritance-tax states and their cliffs.
Sources
IRS Rev. Proc. 2025-32 · SSA Contribution & Benefit Base
Disclaimer
Estimates for general information only, not tax advice. This model applies the 26/28% rates to the whole AMT base and does not separate the preferential capital gains layer. Consult a qualified tax professional, particularly for stock option planning.