Updated October 21, 2026. Quick answer: Worksheet 1-1 in Publication 590-B splits an IRA withdrawal into its tax-free and taxable parts when you made contributions that may not be deductible. Basis plus this year’s contributions, divided by the year-end value plus the distributions, is the tax-free fraction (line 7). Line 8 feeds Form 8606 and line 9 or 11 the taxable amount.
What this worksheet is for
The publication says to use it when you “made contributions to a traditional IRA for 2025 that may not be fully deductible”. The form it feeds is Form 8606, where the same fraction appears at lines 9 to 14 and the result at line 15c.
The worksheet line by line
| Line | What the worksheet says |
|---|---|
| Who uses it | “Use only if you made contributions to a traditional IRA for 2025 that may not be fully deductible and have to figure the taxable part of your 2025 distributions to determine your modified AGI.” |
| 1 | “Enter the basis in your traditional IRAs as of December 31, 2024” |
| 2 | “Enter the total of all contributions made to your traditional IRAs during 2025 and all contributions made during 2026 that were for 2025, whether or not deductible.” |
| 3 | “Add lines 1 and 2” |
| 4 | “Enter the value of all your traditional IRAs as of December 31, 2025” |
| 5 | “Enter the total distributions from traditional IRAs (including amounts converted to Roth IRAs that will be shown on line 16 of Form 8606) received in 2025.” |
| 6 | “Add lines 4 and 5” |
| 7 | “Divide line 3 by line 6. Enter the result as a decimal (rounded to at least three places).” “If the result is 1.000 or more, enter 1.000” |
| 8 | “Nontaxable portion of the distribution.” “Multiply line 5 by line 7. Enter the result here and on lines 13 and 17 of Form 8606” |
| 9 | “Taxable portion of the distribution (before adjustment for conversions).” “Subtract line 8 from line 5.” |
| 10 | “Enter the amount included on line 9 that is allocable to amounts converted to Roth IRAs by December 31, 2025.” |
| 11 | “Taxable portion of the distribution (after adjustments for conversions).” “Subtract line 10 from line 9.” |
The IRS example: Rose Green
Rose has $300 of nondeductible basis from 2024, contributes $2,000 for 2025 and converts $5,000 to a Roth IRA, with $20,000 left in her IRAs at year end. The inputs are the IRS’s; the arithmetic is shown.
| Item | Illustration |
|---|---|
| Line 1: basis at the end of 2024 (the IRS example, Rose Green) | $300 |
| Line 2: contributions for 2025 | $2,000 |
| Line 3, computed: line 1 + line 2 | $2,300 (computed) |
| Line 4: value of all traditional IRAs at the end of 2025 | $20,000 |
| Line 5: distributions in 2025 (all converted to a Roth IRA) | $5,000 |
| Line 6, computed: line 4 + line 5 | $25,000 (computed) |
| Line 7, computed: line 3 divided by line 6 | 0.092 |
| Line 8, computed: line 5 x line 7 | $460 (computed) |
| Line 9, computed: line 5 minus line 8 | $4,540 (computed) |
| Line 10: the part allocable to conversions (all of it) | $4,540 |
| Line 11, computed: line 9 minus line 10 | $0 (computed) |
Line 7 is 2,300 divided by 25,000, which is exactly 0.092, so 9.2 percent of the $5,000 is tax free ($460). The other $4,540 is the taxable part, and because it was all converted by the end of 2025, the worksheet’s line 11 is zero.
Where the lines go
Line 8 goes on Form 8606 lines 13 and 17. The form itself defines the result: “Taxable amount. Subtract line 15b from line 15a.” The publication directs “Enter the amount from line 9 of Worksheet 1-1 (or, if you entered an amount on line 11, the amount from that line) on line 15a of Form 8606.”
A note on conversions
“To figure the percentage, divide the amount converted (from line 16 of Form 8606) by the total distributions shown on line 5.” That percentage times line 9 gives line 10. Roth conversions and the pro rata rule are covered in the backdoor Roth pro rata calculator.
Edition and line numbers
This page reads Publication 590-B (2025), the current file irs.gov served on 2026-10-21 (sha256 in the kit data). The Worksheet 1-1 in it is for the tax year 2025 return, filed in 2026. Check the tax year printed on the worksheet in your own copy and use that year’s line numbers, because a different year’s worksheet can word its lines differently.
Common mistakes
- Using the December 31, 2024 value on line 4. The line asks for the value “as of December 31, 2025”
- Rounding the line 7 decimal to two places. The instruction is “rounded to at least three places”
- Counting a rollover that was completed in the year as a distribution on line 5. The line excludes “any rollovers between traditional IRAs completed by December 31, 2025”
Related: Form 8606, Form 8606 lines 9 to 14, Form 8606 line 15c, and backdoor Roth pro rata calculator.
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Answer againSources
- Publication 590-B (2025), Distributions from Individual Retirement Arrangements (IRAs): https://www.irs.gov/pub/irs-pdf/p590b.pdf
- Form 8606 (2025), Nondeductible IRAs: https://www.irs.gov/pub/irs-pdf/f8606.pdf
Read from the IRS documents linked above on October 21, 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.