Updated October 18, 2026. Quick answer: Line 5 is your AMT exemption, chosen by filing status from the chart printed on the form. Line 6 subtracts line 5 from line 4. Line 7 applies the AMT rates to line 6, or takes the result from Part III when the form says you must complete it.
Line 5: the exemption
The form prints the caption “Exemption.” with a chart by filing status. Read the amounts from that chart on your own copy of the form. This page does not copy the chart. The form adds “If line 4 is over the amount shown above for your filing status, see instructions.”
The instructions say the same thing: “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.” The worksheet is printed in the instructions under the heading Exemption Worksheet, Line 5, and this page points to it by name. Current-year exemption amounts are also on the AMT exemption page.
Form 1040-NR filers: “If you are filing Form 1040-NR, use the following chart to figure the amount to enter on line 5.”
Line 6: subtract the exemption
The form’s line 6 caption reads “Subtract line 5 from line 4. If more than zero, go to line 7.” It continues “If zero or less, enter -0- here and on lines 7, 9, and 11, and go to line 10”. The instructions have no separate paragraph for line 6, so the form’s caption is the guide.
A small computed illustration, not an IRS example, with round numbers chosen only to show the subtraction: if line 4 were $400,000 and line 5 were $100,000, line 6 would be $300,000. The real line 5 comes from the chart for your filing status.
Line 7: the AMT base
Line 7 has three parts on the form. For Form 2555 filers: “If you are filing Form 2555, see instructions for the amount to enter.” The instructions say “If you claimed the foreign earned income exclusion, housing exclusion, or housing deduction on Form 2555, you must use the Foreign Earned Income Tax Worksheet in these instructions to figure the amount to enter on line 7.” Form 2555 itself is explained on the Form 2555 page.
If you have capital gain income of the kinds the form lists: “If you reported capital gain distributions directly on Form 1040 or 1040-SR, line 7; you reported qualified dividends on Form 1040 or 1040-SR, line 3a; or you had a gain on both lines 15 and 16 of Schedule D (Form 1040) (as refigured for the AMT, if necessary), complete Part III on the back and enter the amount from line 40 here.” Part III is on the Part III page.
Everyone else: “All others: If line 6 is $239,100 or less ($119,550 or less if married filing separately), multiply line 6 by 26% (0.26). Otherwise, multiply line 6 by 28% (0.28) and subtract $4,782 ($2,391 if married filing separately) from the result.”
Form 1040-NR filers have a paragraph of their own: “If you are filing Form 1040-NR and you reported capital gain distributions directly on Form 1040-NR, line 7a” begins it. That paragraph sends them to Part III in the same cases, and says “All other Form 1040-NR filers, don’t complete Part III.”
Where the number comes from
Line 5 comes from the chart or the Exemption Worksheet, line 6 is arithmetic on lines 4 and 5, and line 7 comes from the rate sentence above or from Part III. The starting figure, line 4, is explained on the lines 3 and 4 page.
Where it goes next
Line 7 flows into the credit and tax lines. The form says “Tentative minimum tax. Subtract line 8 from line 7.” That is line 9, covered on the lines 8 to 11 page.
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
- Using the chart when line 4 is above it. The 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.”
- Skipping Part III. The form says “complete Part III on the back and enter the amount from line 40 here.”
- Ignoring Form 2555 on line 7. The instructions say “you must use the Foreign Earned Income Tax Worksheet in these instructions to figure the amount to enter on line 7.”
Related: Form 6251, AMT exemption, Form 2555, foreign earned income exclusion and investment income, and Schedule 2 lines 2 and 3.
Sources
- 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.