Updated October 17, 2026. Quick answer: Line 15 of Schedule 1 is the deductible part of self-employment tax, and it comes from Schedule SE. Line 16 is for self-employed SEP, SIMPLE, and qualified plans, and the instructions send you to Pub. 560 for the rules. Both are adjustments for people who work for themselves.
Picking the Schedule C business code for your work (2025 chart): Schedule C code for doctors and dentists.
More IRS forms and schedules, read line by line: Form 5305-SEP instructions and Form 5304-SIMPLE instructions.
Partnership return (Form 1065) for 2025, read line by line: Form 1065 lines 9 and 10 and Form 1065 Schedule K lines 12 to 14.
IRS worksheets from the 2025 Form 1040 instructions, read line by line: Self-Employed Health Insurance Deduction Worksheet.
Schedule C and Schedule SE (Form 1040) for 2025, read line by line: Schedule C lines 17 to 19, Schedule C line 23 and Schedule C lines 31 and 32.
What lines 15 and 16 ask for
The schedule’s captions read “Deductible part of self-employment tax. Attach Schedule SE” for line 15 and “Self-employed SEP, SIMPLE, and qualified plans” for line 16.
Line 15: where the number comes from
The instructions say “If you were self-employed and owe self-employment tax, fill in Schedule SE to figure the amount of your deduction.” They also say where to find it: the deductible part of your self-employment tax “is on line 13 of Schedule SE.” The tax itself is explained on the self-employment tax page, and the business income it is based on is reported on Schedule C.
Line 16: self-employed retirement plans
The instructions say “If you were self-employed or a partner, you may be able to take this” deduction. For the rules they point to a publication: “See Pub. 560 or, if you were a minister, Pub. 517.” The amount is not figured on this schedule. It comes from the plan rules in those publications. Statements about SEP and SIMPLE contributions are discussed on the page for Form 5498 boxes 8, 9 and 10.
Where it goes next
Lines 15 and 16 are part of the adjustments that line 26 adds up: “Add lines 11 through 23 and 25. These are your adjustments to income.” The instructions say “The amount on line 26 is entered on Form 1040, 1040-SR, or 1040-NR, line 10.” Line 17, the health insurance deduction, is the next line and has its own page on line 17. The whole schedule is on the Schedule 1 (Form 1040) page.
Edition and line numbers
This page reads the 2025 Schedule 1 and the 2025 Form 1040 instructions, the current files irs.gov served on 2026-10-17. They are the forms for the tax year 2025 return, filed in 2026. The schedule says “Attach to Form 1040, 1040-SR, or 1040-NR.” Schedule 1 has no separate booklet, because its line instructions sit inside the Form 1040 instructions. 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
- Entering line 15 without Schedule SE. The caption says “Attach Schedule SE”, and the instructions say to “fill in Schedule SE to figure the amount of your deduction.”
- Taking the whole self-employment tax on line 15. The line is for the deductible part of your self-employment tax, which the instructions locate on line 13 of Schedule SE.
- Guessing at line 16 without the plan publication. The instructions say “See Pub. 560 or, if you were a minister, Pub. 517.”
Related: self-employment tax, Schedule C, Form 5498 boxes 8, 9 and 10, and Schedule 1 (Form 1040).
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Answer againSources
- Instructions for Form 1040 and Form 1040-SR (2025): https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
- Schedule 1 (Form 1040), Additional Income and Adjustments to Income (2025): https://www.irs.gov/pub/irs-pdf/f1040s1.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.