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Compute alternative minimum tax and the credit for prior-year minimum tax
Most returns never touch the alternative minimum tax. When one does, the return carries a second computation alongside the regular tax, and the taxpayer owes whichever is higher. This lesson builds that second computation and the credit it can leave behind.
The alternative minimum tax runs beside the regular tax. The return computes regular tax, then recomputes income with a broader base called alternative minimum taxable income (AMTI). It applies exemption and rate steps to reach a tentative minimum tax. The taxpayer owes regular tax plus any excess of tentative minimum tax over regular tax:
\(\text{AMT} = \max(0, \text{tentative minimum tax} - \text{regular tax})\)
Two kinds of items push AMTI above regular taxable income:
| Deferral items | Exclusion items | |
|---|---|---|
| Behavior | Reverse in a later year | Never reverse |
| Example | Incentive stock option timing | State and local tax deduction denied for AMT |
| Future effect | Can support a later minimum tax credit | Never supports the credit |
Sorting each adjustment into one of these two columns determines the rest of the computation. The current liability turns on the total; the later credit turns only on the deferral column. Attach Form 6251 when tentative minimum tax exceeds regular tax; the filing rule also reaches claims for the listed credits — general business, qualified electric vehicle, alternative fuel refueling property, and prior-year minimum tax — and the adjustment case that would otherwise leave tentative above regular. Either way, only the deferral column can later support a minimum tax credit.
Dana has regular tax of $30,000. Her AMT workpaper shows a $60,000 ISO deferral adjustment and a $20,000 state-tax exclusion adjustment, so AMTI is $80,000 above regular taxable income. After exemption and rates, tentative minimum tax is $36,000. AMT is \(36{,}000 - 30{,}000 = 6{,}000\), so total tax is $36,000. The $6,000 liability comes from both columns, but only the deferral portion can later support a credit.
Form 8801 Instructions Specific Instructions
The AMT is a separate tax that is imposed in addition to your regular tax. It is caused by two types of adjustments and preferences—deferral items and exclusion items.View on the source
Form 6251 Instructions Part I—Alternative Minimum Taxable Income (AMTI) / Line 2i—Exercise of Incentive Stock Options
For the regular tax, no income is recognized when an incentive stock option (ISO), as defined in section 422(b), is exercised. However, this rule doesn’t apply for the AMT. Instead, you must generally include on line 2i the excess, if any, of:View on the source
Form 6251 Instructions Part I—Alternative Minimum Taxable Income (AMTI) / Line 2a—Taxes
Enter the amount of all taxes from Schedule A (Form 1040), line 7, except any generation-skipping transfer taxes on income distributions. If you aren’t filing Schedule A (Form 1040), then enter the standard deduction amount that you reported on Form 1040 or 1040-SR, line 12e.View on the source
Form 8801 Instructions Part I—Net Minimum Tax on Exclusion Items / Line 2
Exclusion items are only the following AMT adjustments and preferences: certain itemized deductions (including any investment interest expense reported on Schedule E), certain tax-exempt interest, depletion, the section 1202 exclusion, the standard deduction, and any other adjustments related to exclusion items.View on the source
Form 6251 Instructions General Instructions / Who Must File
Attach Form 6251 to your return if any of the following statements are true. 1. Form 6251, line 7, is greater than line 10.View on the source
Form 6251 Instructions General Instructions / Who Must File
2. You claim any general business credit, and either line 6 (in Part I) of Form 3800 or line 25 of Form 3800 is more than zero. 3. You claim the qualified electric vehicle credit (Form 8834), the personal-use part of the alternative fuel vehicle refueling property credit (Form 8911), or the credit for prior year minimum tax (Form 8801). 4. The total of Form 6251, lines 2c through 3, is negative and line 7 would be greater than line 10 if you didn’t take into account lines 2c through 3.View on the source
A taxpayer's tentative minimum tax (Form 6251, line 7) is $12,000 and regular tax (line 10) is $9,000. What is the AMT?
From AMTI the form subtracts an exemption that depends on filing status, leaving taxable excess. The 2025 starting exemption is $88,100 for single filers, $137,000 for joint and qualifying surviving spouse returns, and $68,500 for married filing separately; the phaseout scale starts at $626,350 of AMTI ($1,252,700 joint), and above that scale the exemption worksheet phases the exemption down. Then the AMT rate schedule applies to taxable excess to reach tentative minimum tax. For 2025, for noncorporate taxpayers, the 26% bracket covers the first $239,100 of taxable excess ($119,550 if married filing separately) and 28% covers the rest, figured on line 7 as 28% of line 6 minus $4,782 ($2,391 if married filing separately). The path is fixed: AMTI, minus exemption after phaseout, equals taxable excess; rates applied to taxable excess equal tentative minimum tax; tentative minimum tax minus regular tax equals AMT.
Ellis files single with AMTI of $300,000 and no phaseout. Exemption is $88,100, so taxable excess is \(300{,}000 - 88{,}100 = 211{,}900\). The full $211,900 falls within the first $239,100 band, so tentative minimum tax is \(211{,}900 \times 26\%\), which is $55,094. If AMTI were $500,000, taxable excess would be $411,900: \(239{,}100 \times 26\%\) is $62,166 and the remaining \(172{,}800 \times 28\%\) is $48,384, so tentative minimum tax is $110,550 — the same as \(411{,}900 \times 28\% - 4{,}782\).
Form 6251 Instructions General Instructions / What’s New
The exemption amount on Form 6251, line 5, has increased to $88,100 ($137,000 if married filing jointly or qualifying surviving spouse; $68,500 if married filing separately).View on the source
Form 6251 Instructions General Instructions / What’s New
For 2025, for noncorporate taxpayers, the 26% tax rate applies to the first $239,100 ($119,550 if married filing separately) of taxable excess (the amount on line 6).View on the source
Form 6251 Instructions General Instructions / What’s New
Also, the amount used to determine the phaseout of your exemption has increased to $626,350 ($1,252,700 if married filing jointly or qualifying surviving spouse).View on the source
Form 6251 Instructions Part II—Alternative Minimum Tax / Line 5—Exemption Amount
If line 4 is more than the amount shown for your filing status in the middle column of the chart on line 5, see the Exemption Worksheet to figure the amount to enter on line 5.View on the source
Form 6251 Instructions Part II—Alternative Minimum Tax / Line 7
Otherwise, figure the amount to enter on line 7 by multiplying line 6 by 28% (0.28) and subtracting $4,782 ($2,391 if married filing separately) from the result.View on the source
A single filer computes 2025 AMTI below the phaseout range. What exemption amount applies?
Paying AMT on timing can prepay tax. When the deferral item reverses for regular tax, the taxpayer may have paid more than the long-run minimum. The minimum tax credit returns that prepayment: the deferral-item portion of prior-year AMT becomes a credit against current regular tax, with unused credit carried forward. The exclusion-item portion never enters this computation. The form is filed only when line 21 is more than zero — when line 21 is zero or less there is no credit or carryforward and the rest of the form is not completed — so most AMT payers with only exclusion items never touch it. The limit then takes three lines. Line 22 starts from this year's regular tax plus Schedule 2 line 1z and subtracts the listed credits, floored at zero. Line 23 is this year's tentative minimum tax (Form 6251, line 9), and line 24 is line 22 minus line 23, floored at zero. The credit on line 25 is the smaller of line 21 or line 24, so the credit can reduce regular tax only down to this year's tentative minimum tax; the rest carries forward.
Last year Finn paid $9,000 of AMT, of which $7,000 traced to an ISO deferral item and $2,000 to state-tax exclusion items. This year his regular tax before credits is $40,000 and tentative minimum tax is $38,000. The $7,000 deferral portion is available as a minimum tax credit, but it can bring regular tax down only to this year's tentative minimum tax. With no other credits, line 22 is $40,000, line 23 is $38,000, and line 24 is \(40{,}000 - 38{,}000 = 2{,}000\). Finn uses $2,000 this year and carries the remaining $5,000 forward. The $2,000 exclusion portion supports no credit.
Form 8801 Instructions General Instructions / Purpose of Form
Use Form 8801 if you are an individual, estate, or trust to figure the minimum tax credit, if any, for alternative minimum tax (AMT) you incurred in prior tax years and to figure any credit carryforward to 2026.View on the source
Form 8801 Instructions Specific Instructions
The minimum tax credit is allowed only for the AMT caused by deferral items.View on the source
Form 8801 Instructions General Instructions / Who Should File
File Form 8801 only if line 21 is more than zero.View on the source
Form 8801 Instructions Part II—Minimum Tax Credit and Carryforward to 2026 / Line 21
If line 21 is zero or less, you don't have a minimum tax credit or a credit carryforward. Don't complete the rest of this form and don't file it.View on the source
Form 8801 Instructions Part II—Minimum Tax Credit and Carryforward to 2026 / Line 22
Add the amounts from Form 1040, 1040-SR, or 1040-NR, line 16 and Schedule 2 (Form 1040), line 1z. Subtract from the result the total of any credits from Form 1040, 1040-SR, or 1040-NR, line 19 and Schedule 3 (Form 1040), lines 1 through 6z (not including any credit for prior year minimum tax on line 6b or any credit claimed on Form 8912, Credit to Holders of Tax Credit Bonds, on line 6k). Enter the result. If the result is zero or less, enter -0-.View on the source
A taxpayer paid $10,000 of AMT: $8,000 from an incentive stock option timing adjustment and $2,000 from the disallowed standard deduction. What minimum tax credit does that payment generate?
The course asks you questions like these as you learn, brings back the ones you miss, and ends with full-length practice exams.
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