Updated October 28, 2026. Quick answer: The Exemption Worksheet in the Form 6251 instructions figures the line 5 exemption when your AMT income is above the starting point for your filing status. It takes 25 cents off the exemption for every dollar of AMT income above $626,350 (single, head of household or married filing separately) or $1,252,700 (married filing jointly or qualifying surviving spouse).
When you use it
The Form 6251 instructions say “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.” Below that point the chart on the form gives the exemption directly. The form’s own line reads “Exemption.” The line-level walkthrough is at Form 6251 lines 5 to 7.
The worksheet line by line
| Line | What the worksheet says |
|---|---|
| Note | “Note: If Form 6251, line 4, is equal to or more than $978,750 if single or head of household, $1,800,700 if married filing jointly or qualifying surviving spouse, or $900,350 if married filing separately, your exemption is zero.” |
| 1 | “Enter $88,100 if single or head of household; $137,000 if married filing jointly or qualifying surviving spouse; or $68,500 if married filing separately” |
| 2 | “Enter your alternative minimum taxable income (AMTI) from Form 6251, line 4” |
| 3 | “Enter $626,350 if single or head of household; $1,252,700 if married filing jointly or qualifying surviving spouse; or $626,350 if married filing separately” |
| 4 | “Subtract line 3 from line 2. If zero or less, enter -0-” |
| 5 | “Multiply line 4 by 25% (0.25)” |
| 6 | “Subtract line 5 from line 1. If zero or less, enter -0-.” “Also, enter this amount on Form 6251, line 5, and go to Form 6251, line 6” |
The 2025 figures it uses
| Filing status | Line 1 exemption | Line 3 starting point | Exemption is zero at |
|---|---|---|---|
| Single or head of household | $88,100 | $626,350 | $978,750 |
| Married filing jointly or qualifying surviving spouse | $137,000 | $1,252,700 | $1,800,700 |
| Married filing separately | $68,500 | $626,350 | $900,350 |
The zero point, recomputed
The zero point in the note is not a separate rule. It is where line 5 of the worksheet has used up the whole exemption, so it equals line 1 divided by 0.25, plus line 3. Single or head of household: $88,100 divided by 0.25 is $352,400 (computed), and $352,400 plus $626,350 is $978,750 (computed). Married filing jointly: $137,000 divided by 0.25 is $548,000 (computed), and $548,000 plus $1,252,700 is $1,800,700 (computed). Married filing separately: $68,500 divided by 0.25 is $274,000 (computed), and $274,000 plus $626,350 is $900,350 (computed). All three match the figures the IRS prints.
A worked example
Illustration, not an IRS example. For the computation below, a single filer is assumed to have alternative minimum taxable income of $666,350 on Form 6251 line 4.
| Item | Illustration |
|---|---|
| Line 1: single filer’s base exemption | $88,100 |
| Line 2: AMTI from Form 6251 line 4 (an invented input for the computation) | $666,350 |
| Line 3: single filer’s starting point | $626,350 |
| Line 4, computed: line 2 minus line 3 | $40,000 (computed) |
| Line 5, computed: line 4 x 0.25 | $10,000 (computed) |
| Line 6, computed: line 1 minus line 5, to Form 6251 line 5 | $78,100 (computed) |
The exemption falls from $88,100 to $78,100 because $40,000 of AMT income above the starting point costs $10,000 of exemption.
Married filing separately: line 4 first
The instructions for line 4 add an amount before the worksheet starts: “If your filing status is married filing separately and line 4 is more than $900,350, you must include an additional amount on line 4.” Do that first, because line 2 of the worksheet is the line 4 you end up with.
Edition
This page reads the Instructions for Form 6251 (2025), the file irs.gov served on 2026-10-28 (sha256 in the kit data). It covers the 2025 return, filed in 2026. Check the tax year printed on the worksheet in your own copy and use that year’s line numbers and dollar amounts, because a different year’s worksheet can word its lines differently.
Common mistakes
- Using the worksheet when line 4 is at or below the middle-column amount in the chart. The chart gives the exemption directly there.
- Forgetting that the exemption can reach zero. Line 6 is “If zero or less, enter -0-.”
- Using another year’s figures. The exemption, the starting point and the zero point all move each year.
Related: Form 6251 lines 5 to 7, AMT exemption for 2026, AMT exemption for 2027, and Form 6251.
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Answer againSources
- Instructions for Form 6251 (2025), Alternative Minimum Tax, Individuals: https://www.irs.gov/pub/irs-pdf/i6251.pdf
- Form 6251 (2025), Alternative Minimum Tax, Individuals: https://www.irs.gov/pub/irs-pdf/f6251.pdf
Read from the IRS documents linked above on October 28, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.