Updated October 17, 2026. Quick answer: Line 12 is the credit for federal excise taxes paid on fuels that were ultimately used for a nontaxable purpose. You attach Form 4136, which is where the figure comes from. The amount is added into line 15 of Schedule 3.
What line 12 is
The schedule captions it “Credit for federal tax on fuels. Attach Form 4136”, in Part II, “Other Payments and Refundable Credits”. The instructions give the heading “Credit for Federal Tax on Fuels”.
What goes on line 12 and where the number comes from
The instruction reads: “Enter any credit for federal excise taxes paid on fuels that are ultimately used for a nontaxable purpose”. The instructions end the paragraph with “Attach Form 4136.” The figure on line 12 is therefore the credit worked out on Form 4136, not a number you derive on Schedule 3 itself.
Where it goes next
Line 12 is one of the amounts added on line 15. The schedule describes line 15 as “Add lines 9 through 12 and 14. Enter here and on Form 1040, 1040-SR, or 1040-NR, line 31”. The General Instructions repeat it: “Enter the amount on Schedule 3, line 15, on Form 1040, 1040-SR, or 1040-NR, line 31.” See the Form 1040 lines 29, 30 and 31 page for the Form 1040 side. The previous line is covered on Schedule 3 line 11 and the next lines on Schedule 3 lines 13a to 13d.
Edition and line numbers
This page reads the 2025 Schedule 3 (Form 1040) and the 2025 Form 1040 instructions, the current files irs.gov served on 2026-10-17. They are the files for the tax year 2025 return, filed in 2026. The schedule says “Attach to Form 1040, 1040-SR, or 1040-NR.” Its line instructions are part of the Form 1040 instructions, under the heading “Instructions for Schedule 3”. Check the tax year printed on the schedule you are filling in and use the line numbers on that year’s schedule, because a different year’s schedule can number or word its lines differently.
Common mistakes
- Claiming the credit without the form. The line caption reads “Credit for federal tax on fuels. Attach Form 4136”.
- Treating any fuel purchase as qualifying. The instructions limit the line to “federal excise taxes paid on fuels that are ultimately used for a nontaxable purpose”.
- Entering the amount on the wrong Form 1040 line. The instruction is “Enter the amount on Schedule 3, line 15, on Form 1040, 1040-SR, or 1040-NR, line 31.”
Related: Form 1040 lines 29, 30 and 31, Form 1040 line by line, and Form 1040.
Sources
- Instructions for Form 1040 and Form 1040-SR (2025): https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
- Schedule 3 (Form 1040), Additional Credits and Payments (2025): https://www.irs.gov/pub/irs-pdf/f1040s3.pdf
Read from the IRS documents linked above on October 17, 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.