Updated October 18, 2026. Quick answer: Part III figures the AMT with the lower capital gains rates when line 7 sends you there. Line 12 starts from line 6, lines 13 to 15 pull capital gain amounts from your regular tax worksheets, and line 40 returns the result to line 7. The form prints every step, so you mostly follow its captions.
Who completes Part III
The heading reads “Tax Computation Using Maximum Capital Gains Rates”. “Complete Part III only if you are required to do so by line 7 or by the Foreign Earned Income Tax Worksheet in the instructions.” Line 7 is on the lines 5 to 7 page. The worksheet most filers pull from is explained on the Qualified Dividends and Capital Gain Tax Worksheet page.
Lines 13 to 15: which numbers to use
The instructions begin “Determine if any of the following statements apply.” Statement 1 reads “The gain or loss from any transaction reported on Form 8949 or Schedule D is different for the AMT”. Statement 2 reads “You didn’t complete either the Qualified Dividends and Capital Gain Tax Worksheet or the Schedule D Tax Worksheet because Form 1040, 1040-SR, or 1040-NR, line 15, is zero.” Statement 3 reads “You received a Schedule K-1 (Form 1041) that shows an amount in box 12 with code B, C, D, E, or F.”
If none applies: “Use the regular tax amounts to complete lines 13, 14, and 15.” If one applies, the instructions lay out steps that include an AMT Form 8949 or AMT Schedule D, and they close with “Keep the AMT Form 8949, AMT Schedule D, and the applicable AMT worksheet for your records but don’t attach any of them to your tax return.” Form 8949 is on the Form 8949 page, and line 7 of the Form 1040 is on the capital gain or loss page.
The lines, in order
These are the captions printed on the form. Lines 19 and 25 print filing-status amounts in a list, and this page leaves those amounts on the form. Read them from your own copy.
| Line | What the form says |
|---|---|
| 12 | “Enter the amount from Form 6251, line 6.” |
| 13 | “Enter the amount from line 4 of the Qualified Dividends and Capital Gain Tax Worksheet in the Instructions for Form 1040” |
| 14 | “Enter the amount from Schedule D (Form 1040), line 19 (as refigured for the AMT, if necessary).” |
| 15 | “add lines 13 and 14, and enter the smaller of that result or the amount from line 10 of the Schedule D Tax Worksheet” |
| 16 | “Enter the smaller of line 12 or line 15” |
| 17 | “Subtract line 16 from line 12” |
| 18 | “If line 17 is $239,100 or less ($119,550 or less if married filing separately), multiply line 17 by 26% (0.26).” |
| 20 | “Enter the amount from line 5 of the Qualified Dividends and Capital Gain Tax Worksheet or the amount from line 14 of the Schedule D Tax Worksheet, whichever applies (as figured for the regular tax).” |
| 21 | “Subtract line 20 from line 19. If zero or less, enter -0-” |
| 22 | “Enter the smaller of line 12 or line 13” |
| 23 | “Enter the smaller of line 21 or line 22. This amount is taxed at 0%” |
| 24 | “Subtract line 23 from line 22” |
| 26 to 29 | “Add line 26 and line 27” and “Subtract line 28 from line 25. If zero or less, enter -0-” |
| 30 and 31 | “Enter the smaller of line 24 or line 29” then “Multiply line 30 by 15% (0.15)” |
| 32 | “Add lines 23 and 30” |
| 33 and 34 | “Subtract line 32 from line 22” then “Multiply line 33 by 20% (0.20)” |
| 35 to 37 | “Add lines 17, 32, and 33”, “Subtract line 35 from line 12”, “Multiply line 36 by 25% (0.25)” |
| 38 | “Add lines 18, 31, 34, and 37” |
| 39 | “If line 12 is $239,100 or less ($119,550 or less if married filing separately), multiply line 12 by 26% (0.26).” |
| 40 | “Enter the smaller of line 38 or line 39 here and on line 7.” |
Form 2555 and Form 1040-NR
“Form 2555. If you are filing Form 2555 and you have an AMT capital gain excess, you must complete Part III of Form 6251 with certain modifications.” The form’s line 40 caption adds “If you are filing Form 2555, do not enter this amount on line 7.” “Instead, enter it on line 4 of the worksheet in the instructions for line 7”. Form 1040-NR filers have separate paragraphs under several lines. For line 13: “If you are filing Form 1040-NR, enter on Form 6251, line 13” begins theirs.
Where the number comes from
Lines 13 and 14 come from your regular tax worksheets and Schedule D, with AMT changes only if a statement above applies. Line 12 comes from line 6. Everything else is arithmetic on those.
Where it goes next
Line 40 returns to line 7: “Enter the smaller of line 38 or line 39 here and on line 7.” The credit and AMT lines that follow are on the lines 8 to 11 page. If you are weighing how the timing of gains affects this part of the return, the long-term capital gains brackets page is a starting point.
Edition and line numbers
This page reads the 2025 Form 6251 and its 2025 instructions, the current files irs.gov served on 2026-10-18. They are the files for the tax year 2025 return, filed in 2026. The form’s own header says “Attach to Form 1040, 1040-SR, or 1040-NR.” Check the tax year printed on the form you are filling in and use the line numbers on that year’s form, because a different year’s form can number or word its lines differently.
Common mistakes
- Completing Part III when it is not required. The form says “Complete Part III only if you are required to do so by line 7 or by the Foreign Earned Income Tax Worksheet in the instructions.”
- Attaching the AMT worksheets. The instructions say “Keep the AMT Form 8949, AMT Schedule D, and the applicable AMT worksheet for your records but don’t attach any of them to your tax return.”
- Entering line 40 on line 7 when you file Form 2555. The form says “If you are filing Form 2555, do not enter this amount on line 7.”
Related: Form 6251, Qualified Dividends and Capital Gain Tax Worksheet, Form 8949, capital gain or loss, and long-term capital gains brackets.
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- Instructions for Form 6251, Alternative Minimum Tax, Individuals (2025): https://www.irs.gov/pub/irs-pdf/i6251.pdf
- Form 6251, Alternative Minimum Tax, Individuals (2025): https://www.irs.gov/pub/irs-pdf/f6251.pdf
Read from the IRS documents linked above on October 18, 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.