Updated October 18, 2026. Quick answer: Line 1 is where you enter the nondeductible contributions you made to traditional IRAs for 2025. The number usually comes from the IRA deduction worksheet in the Form 1040 instructions, or from the worksheet in Pub. 590-A if your deduction was reduced. If you made no deductible contributions, it is your nondeductible contributions up to your contribution limit.
IRS worksheets read line by line: Pub 590-B Worksheet 1-1.
What line 1 asks for
The form’s caption reads “Enter your nondeductible contributions to traditional IRAs for 2025, including those made for 2025 from January 1, 2026, through April 15, 2026.” So the line covers contributions made for 2025 even if you made them in the first months of 2026. The form’s own heading for Part I says to complete it if “You made nondeductible contributions to a traditional IRA for 2025.” The full Form 8606 is explained on the Form 8606 page.
Where the number comes from
The instructions give three starting points. If you used the IRA deduction worksheet in the Form 1040 instructions, they say to “subtract line 12 of the worksheet (or the amount you chose to deduct on Schedule 1 (Form 1040), line 20, if less) from the smaller of line 10 or line 11 of the worksheet.” The result goes on line 1. The deduction itself is covered on the Schedule 1 line 20 page.
If you used the other worksheet, the instructions say “enter on line 1 of Form 8606 any nondeductible contributions from the appropriate lines of that worksheet.” If you took no deduction, they say “you can make nondeductible contributions up to your contribution limit”, and to “Enter on line 1 of Form 8606 your nondeductible contributions.” The limit is explained on the IRA contribution limit page.
What to add and what to leave out
Two further rules apply. “Include on line 1 any repayment of a qualified reservist distribution.” And the instructions warn: “Don’t include on line 1 contributions that you had returned to you with the related earnings (or less any loss).” Employer money is also a different category. The form says nondeductible contributions “do not include employer contributions made to a SEP IRA pursuant to a SEP arrangement or to a SIMPLE IRA pursuant to a SIMPLE IRA plan.” The contribution amounts your IRA custodian reports are covered on the Form 5498 box 1 page.
Where it goes next
Line 1 is added to your starting basis on line 3. The form says “Add lines 1 and 2”. Line 2 is explained on the Form 8606 line 2 page and the sum on the lines 3, 4 and 5 page. The instructions also say “You can’t deduct the amount included on line 1.”
Edition and line numbers
This page reads the 2025 Form 8606 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 says “Attach to 2025 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
- Including contributions that were taken back out. The instructions say “Don’t include on line 1 contributions that you had returned to you with the related earnings (or less any loss).”
- Treating a SEP or SIMPLE employer contribution as nondeductible. The form says nondeductible contributions “do not include employer contributions made to a SEP IRA pursuant to a SEP arrangement or to a SIMPLE IRA pursuant to a SIMPLE IRA plan.”
- Forgetting that the line includes early 2026 contributions made for 2025. The caption says “including those made for 2025 from January 1, 2026, through April 15, 2026.”
Related: Form 8606, Schedule 1 line 20, IRA contribution limit, and Form 5498 box 1.
Sources
- Instructions for Form 8606, Nondeductible IRAs (2025): https://www.irs.gov/pub/irs-pdf/i8606.pdf
- Form 8606, Nondeductible IRAs (2025): https://www.irs.gov/pub/irs-pdf/f8606.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.