Updated October 2, 2026. Quick answer: You file Form 8606 when you make a nondeductible contribution to a traditional IRA, take a traditional IRA distribution while you have basis, convert to a Roth IRA, or take a Roth IRA distribution. It tracks the after-tax money in your IRAs so it is not taxed twice. Skipping it when it is required for a nondeductible contribution carries a $50 penalty unless you show reasonable cause. A backdoor Roth conversion always puts a Form 8606 on the return.
IRS worksheets read line by line: Pub 590-B Worksheet 1-1.
Business use of your home (Form 8829), the saver’s credit (Form 8880), clean vehicle credits (Form 8936) and amended returns (Form 1040-X), read line by line: Form 8880, Form 8880 lines 1 to 5 and Form 1040-X lines 1 to 3.
Form 8606 and Form 8889 for 2025, read line by line: Form 8606 line 6, Form 8606 line 7 and Form 8606 line 8.
Schedule 2 (Form 1040) for 2025, read line by line: Schedule 2 line 8.
Schedule 1 (Form 1040) for 2025, read line by line: Schedule 1 line 20.
Form 5329 for 2025, read code by code: Form 5329 exception code 08, Form 5329 exception code 09 and Form 5329 exception code 21.
Read box by box from the IRS form text: Form 1099-R box 1, Form 1099-R box 5 and the 1099-R IRA/SEP/SIMPLE checkbox.
Form 1040 for 2025, read line by line: Form 1040 lines 4a and 4b, Form 1040 line 5a and 5b and Form 1040 line 6a and 6b.
More IRS forms and schedules, read line by line: Form 4506-T instructions.
Related reading on this site: IRA contribution deadline 2026 and Roth conversion deadline 2026.
More IRS forms and schedules, read line by line: Form 1040 instructions and Form 8888 instructions.
More IRS forms and schedules, read line by line: Schedule 1 (Form 1040) guide.
Price an IRA withdrawal against the 2026 brackets: IRA withdrawal calculator.
Who must file Form 8606
The instructions open the test with “File 2025 Form 8606 if any of the following apply.” The situations that matter most to retirement savers are:
- “You made nondeductible contributions to a traditional IRA for 2025.”
- “You received distributions from a traditional IRA in 2025 and your basis in these IRAs is more than zero.”
- “You converted an amount from a traditional IRA to a Roth IRA in 2025.”
- “You received distributions from a Roth IRA in 2025”, other than a rollover, recharacterization, or return of certain contributions.
Two limits keep the form off some returns. “You don’t have to file Form 8606 solely to report regular contributions to Roth IRAs.” And for distributions: “If you received distributions from a traditional IRA in 2025 and you have never made nondeductible contributions (including nontaxable amounts you rolled over from a qualified retirement plan) to these IRAs, don’t report the distributions on 2025 Form 8606.”
It travels with the return: “File 2025 Form 8606 with your 2025 Form 1040, 1040-SR, or 1040-NR by the due date, including extensions, of your return.” Spouses do not share a form: “If both you and your spouse are required to file 2025 Form 8606, file a separate 2025 Form 8606 for each of you.”
The 2025 form and instructions are the revision the IRS serves as of October 2, 2026, and they apply to returns filed in 2026. A later revision may renumber lines, so check the line numbers against the form in front of you.
Part I: nondeductible contributions and basis
Part I covers contributions and, when you take money out, the taxable share of it. On the amount that goes on line 1: “If you didn’t have any deductible contributions, you can make nondeductible contributions up to your contribution limit”. The instruction for line 1 for that case is “Enter on line 1 of Form 8606 your nondeductible contributions.”
Basis is the running total the form exists to protect: “Your basis in traditional IRAs is the total of all your nondeductible contributions and your nontaxable amounts included in rollovers made to these IRAs minus the total of all your nontaxable distributions, adjusted if necessary” The IRS adds: “Keep track of your basis to figure the nontaxable part of your future distributions.”
Line 2 carries the prior balance forward. “Generally, if this is the first year you are required to file Form 8606, enter -0-.” Otherwise the Total Basis Chart in the instructions points to a line on your last filed form; for a last form filed for a year after 2023 and before 2025 it is the line 14 amount, with a possible adjustment. SEP and SIMPLE money is outside this: “Nondeductible contributions to a traditional IRA do not include employer contributions” made to a SEP IRA or SIMPLE IRA.
The pro rata lines, 6 through 14
When you take a distribution or make a conversion in a year you also hold pre-tax IRA money, the form blends your basis across all your traditional IRAs. Three inputs feed that blend. Line 6: “Enter the total value of all your traditional IRAs as of December 31, 2025, plus any outstanding rollovers.” Line 7 is the year’s distributions, and the instructions list items to leave off, starting with “Distributions that you converted to a Roth IRA.” Line 8: “If, in 2025, you converted any amounts from traditional IRAs to a Roth IRA, enter on line 8 the net amount you converted.”
The instructions do not walk through lines 9 to 13, the arithmetic that sets the nontaxable share, and they do not use the phrase pro rata. For that computation they send you elsewhere: “For details, including how to complete Form 8606, see Are Distributions Taxable? in chapter 1 of Pub. 590-B.” Publication 590-A’s record-keeping worksheet labels the nontaxable amount as Form 8606, line 13, and basis as line 14. Line 14 is defined this way: “Enter the amount on line 3 reduced by the amount on line 13.”
To see the effect with your own balances, use the backdoor Roth pro rata calculator. Clearing pre-tax balances before a conversion is covered on the December 31 pre-tax IRA fix.
For the taxable amount on line 15c, when the repayment worksheet is not needed, the instructions say to enter “the amount on 2025 Form 8606, line 15a, reduced by the amount on 2025 Form 8606, line 15b.” The additional tax for early distributions is separate, and the instructions note “there is generally an additional 10% tax on the portion of the distribution that is included in income” for people younger than the stated age.
Part II: conversions to a Roth IRA
“Complete Part II if you converted part or all of your traditional IRAs to a Roth IRA in 2025.” A backdoor Roth is a nondeductible traditional contribution followed by a conversion, so it uses Part I for the contribution and Part II for the conversion. The form decides how much of the conversion is taxable. On line 18: “If your entry on line 18 is zero or less, don’t include the result on 2025 Form 1040, 1040-SR, or 1040-NR, line 4b.” The full amount still goes on line 4a.
A conversion is final for these purposes: “A conversion of a traditional IRA to a Roth IRA, and a rollover from any other eligible retirement plan to a Roth IRA, made in tax years beginning after December 31, 2017, cannot be recharacterized as having been made to a traditional IRA.”
A related case with its own page: inherited IRA basis on Form 8606.
Part III: Roth IRA distributions
“Complete Part III to figure the taxable part, if any, of your 2025 Roth IRA distributions.” The instructions describe the Roth IRA this way: “Qualified distributions aren’t includible in income.” If nothing needs to go on line 19, the rule is: “If, after considering the items above, you don’t have an amount to enter on line 19, don’t complete Part III; your Roth IRA distribution(s) isn’t taxable.”
Roth contributions are limited by income. The 2025 modified AGI limits printed in the instructions are below.
| Filing status | 2025 Roth IRA modified AGI limit (less than) |
|---|---|
| Married filing jointly or qualifying surviving spouse | $246,000 |
| Single, head of household, or married filing separately and did not live with spouse | $165,000 |
| Married filing separately and lived with spouse at any time in 2025 | $10,000 |
Lines at a glance, and the penalty for not filing
| Form 8606 | What the 2025 instructions say it holds |
|---|---|
| Line 1 | Nondeductible contributions for the year |
| Line 2 | Basis carried from your last filed Form 8606 |
| Line 6 | Value of all traditional IRAs at year end, plus outstanding rollovers |
| Line 7 | Distributions for the year, minus listed exclusions |
| Line 8 | Net amount converted to a Roth IRA |
| Line 14 | The amount on line 3 reduced by the amount on line 13 |
| Part II | Conversions to Roth IRAs |
| Part III | Distributions from Roth IRAs |
The penalty is stated in two parts. “If you are required to file Form 8606 to report a nondeductible contribution to a traditional IRA for 2025 but don’t do so, you must pay a $50 penalty, unless you can show reasonable cause.” “If you overstate your nondeductible contributions, you must pay a $100 penalty, unless you can show reasonable cause.”
A filed return can be fixed: “Generally, after you file your return, you can change a nondeductible contribution to a traditional IRA to a deductible contribution or vice versa if you make the change within the time limit for filing Form 1040-X”.
Every Form 8606 line page in one table
Each row links to the page that reads a line, or group of lines, of Form 8606. The right column is the summary each page carries.
| Page | What it covers |
|---|---|
| Form 8606 Line 1: Nondeductible IRA Contributions (2025) | How Form 8606 line 1 works on the 2025 return: your nondeductible traditional IRA contributions, where the number comes from, and what to leave out. |
| Form 8606 Line 2: Total Basis in Traditional IRAs (2025) | How Form 8606 line 2 works on the 2025 return: your total basis in traditional IRAs, the Total Basis Chart, and when the amount differs from the chart. |
| Form 8606 Lines 3, 4 and 5: Totals and April Contributions | How Form 8606 lines 3, 4 and 5 work on the 2025 return: adding lines 1 and 2, the yes or no question, and subtracting contributions made by April 15, 2026. |
| Form 8606 Line 6: Value of Traditional IRAs Dec 31 (2025) | How Form 8606 line 6 works on the 2025 return: the year-end value of all your traditional IRAs, outstanding rollovers, and recharacterizations. |
| Form 8606 Line 7: Distributions From Traditional IRAs | How Form 8606 line 7 works on the 2025 return: your traditional IRA distributions and the items the instructions say to leave off the line. |
| Form 8606 Line 8: Net Amount Converted to Roth IRAs | How Form 8606 line 8 works on the 2025 return: the net amount you converted from traditional IRAs to Roth IRAs and the line it is copied to. |
| Form 8606 Lines 9 to 14: Pro-Rata Fraction and Basis | How Form 8606 lines 9 to 14 work on the 2025 return: the pro-rata fraction, the nontaxable portions of distributions and conversions, and remaining basis. |
| Form 8606 Lines 15a and 15b: Disaster Distributions (2025) | How Form 8606 lines 15a and 15b work on the 2025 return: subtracting line 12 from line 7, and the qualified disaster distribution amount on line 15b. |
| Form 8606 Line 15c: Taxable Amount of IRA Distributions (2025) | How Form 8606 line 15c works on the 2025 return: the taxable amount, the 2025 Line 15c Worksheet, and the Form 1040 line 4b entry. |
| Form 8606 Lines 16, 17 and 18: Roth Conversions (2025) | How Form 8606 lines 16, 17 and 18 work on the 2025 return: the converted amount, its basis, and the taxable amount that goes to Form 1040 line 4b. |
| Form 8606 Lines 19 and 20: Roth IRA Distributions (2025) | How Form 8606 lines 19 and 20 work on the 2025 return: nonqualified Roth IRA distributions, what to leave off line 19, and first-time homebuyer expenses. |
| Form 8606 Lines 21, 22 and 23: Roth Contribution Basis (2025) | How Form 8606 lines 21, 22 and 23 work on the 2025 return: subtracting homebuyer expenses, your Roth contribution basis, and the additional tax. |
| Form 8606 Lines 24 and 25a: Conversion Basis (2025 Return) | How Form 8606 lines 24 and 25a work on the 2025 return: your basis in Roth conversions and rollovers, and the subtraction on line 25a. |
| Form 8606 Lines 25b and 25c: Taxable Roth Amount (2025) | How Form 8606 lines 25b and 25c work on the 2025 return: qualified disaster distributions from a Roth IRA, the 2025 Line 25c Worksheet, and the taxable amount. |
Common mistakes
- Not filing Form 8606 for the year of a nondeductible contribution because the contribution was converted right away. Contribution and conversion both belong on the form.
- Forgetting that basis carries forward. A skipped year leaves line 2 without a reliable starting number and risks taxing the same money twice.
- Reporting only the converted amount and ignoring pre-tax IRA balances. Line 6 counts the total value of all traditional IRAs, not just the account you converted from.
Related: the backdoor Roth pro rata calculator, inherited IRA basis on Form 8606, clearing pre-tax IRA money before a backdoor Roth, and Form 5329 explained.
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Answer againSources
- Instructions for Form 8606 (2025): https://www.irs.gov/pub/irs-pdf/i8606.pdf
- IRS Publication 590-A, Contributions to IRAs (2025): https://www.irs.gov/pub/irs-pdf/p590a.pdf
Read from the IRS documents linked above on October 2, 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.