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FreeTY 2025Form 6251

AMT Calculator (Form 6251)

Determine your Alternative Minimum Tax exposure for tax year 2025. Calculates AMTI, exemption with phase-out, tentative minimum tax at 26%/28%, and the AMT owed (if any) above your regular tax liability.

Step 1 of 3

Your filing status & base figures

Filing statusDetermines exemption amount and bracket thresholds

Regular taxable income (Form 1040 line 15)AGI minus standard or itemized deduction, before QBI

Regular tax liability (Form 1040 line 16)Calculated tax before credits

Step 2 of 3

AMT preferences & adjustments

Add back the items disallowed for AMT. Check each that applies and enter the amount. Under TCJA (still in effect through 2025) several common pre-2018 preferences are suspended — they're noted below.

State & local taxes (SALT) deduction

Add back the SALT itemized deduction. Capped at $10K/$40K under TCJA/OBBBA — but still 100% added back for AMT.

Incentive Stock Option (ISO) bargain element

FMV at exercise minus strike price, for ISOs exercised and held in 2025. Common AMT trigger.

Excess depletion (oil & gas)

Percentage depletion in excess of property basis

Tax-exempt interest from private activity bonds

PAB interest is regular-tax-exempt but AMT-taxable for non-grandfathered bonds

Depreciation difference

Excess of regular MACRS over AMT depreciation (typically ADS straight-line for AMT)

Other AMT adjustments

Net operating loss, passive activity, long-term contracts, etc.

Suspended through 2025 (TCJA): personal exemption add-back, miscellaneous itemized deductions, standard deduction add-back. These return only if TCJA provisions sunset — OBBBA permanently extended most individual provisions, so these likely remain suspended.

Result

Your AMT calculation

Regular taxable income$0

+ AMT preferences$0

= AMTI before exemption$0

− AMT exemption (after phase-out)$0

= AMTI taxable base$0

Tentative minimum tax$0

− Regular tax liability$0

Alternative Minimum Tax owed$0

No AMT exposure based on inputs

📐 2025 AMT Parameters

Exemption — Single/HoH$88,100

Exemption — MFJ$137,000

Exemption — MFS$66,650

26% / 28% threshold (MFJ, S, HoH)$232,600

26% / 28% threshold (MFS)$116,300

Phase-out starts (MFJ)$1,218,700

Phase-out starts (Single/HoH)$609,350

💡 AMT Quick Facts

AMT is a parallel tax system. You owe the higher of regular tax or AMT.

TCJA dramatically reduced AMT impact — under 200K returns owed AMT in 2023 vs ~5M before TCJA.

Most common modern trigger: ISO exercises with bargain element > AMT exemption.

AMT paid generates a credit (Form 8801) carryforward usable against future regular tax.

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How the Alternative Minimum Tax is calculated

The AMT is a parallel tax system that ensures higher-income taxpayers with large deductions or preference items still pay a minimum amount. You compute your tax twice — once under the regular rules and once under the AMT rules on Form 6251 — and pay whichever is higher. To get alternative minimum taxable income (AMTI) you start from regular taxable income and add back items the AMT disallows, most commonly the state and local tax deduction, along with adjustments such as the bargain element on incentive stock options.

For 2025 the AMT exemption is $88,100 for single and head-of-household filers, $137,000 for married filing jointly, and $68,500 for married filing separately. The exemption phases out by 25 cents per dollar of AMTI above $626,350 (single/HoH) or $1,252,700 (joint). AMT is then 26% of net AMTI up to $239,100 ($119,550 for MFS) and 28% above that.

Worked example

A married couple has $700,000 of AMTI for 2025, mostly from exercising incentive stock options. Their $137,000 exemption is not yet reduced because AMTI is below the $1,252,700 phase-out start. Net AMTI is $700,000 − $137,000 = $563,000. The tentative minimum tax is 26% × $239,100 + 28% × ($563,000 − $239,100) = $62,166 + $90,692 = $152,858. If their regular tax is $140,000, they owe $12,858 of AMT on top.

Common mistakes & edge cases

The classic modern AMT trigger is exercising and holding incentive stock options: the spread between the strike price and the fair market value is an AMT preference even though it is not regular-tax income that year. Long-term capital gains and qualified dividends keep their preferential rates under the AMT, so they rarely cause AMT by themselves, but they raise AMTI and can erode the exemption. OBBBA made the higher TCJA exemption amounts permanent but, beginning in 2026, lowered the exemption phase-out starting points to $500,000 (single) and $1,000,000 (joint), which will pull more high earners into AMT.

Frequently asked questions

What is the AMT exemption for 2025?

$88,100 for single and head-of-household filers, $137,000 for married filing jointly, and $68,500 for married filing separately, with a 25%-per-dollar phase-out beginning at $626,350 of AMTI (single/HoH) and $1,252,700 (joint).

What commonly triggers the AMT?

Exercising incentive stock options and holding the shares is the most common trigger today, because the bargain element is an AMT preference. Large state and local tax deductions, certain accelerated depreciation, and private-activity-bond interest also add to AMTI.

Did OBBBA change the AMT?

Yes. The One Big Beautiful Bill Act made the elevated TCJA exemption amounts permanent, but it lowered the exemption phase-out thresholds starting in 2026 to $500,000 (single) and $1,000,000 (joint), expanding AMT exposure for upper-income filers in future years.