Form 8606: How to Report Nondeductible IRA Contributions and Roth Conversions

Form 8606, Nondeductible IRAs, tracks money inside your IRAs that you already paid tax on. File it and that money comes out tax free; skip it and you risk double taxation.

This guide is for anyone who made a traditional IRA contribution that wasn’t deductible, did a backdoor Roth or other conversion, or took a nonqualified Roth withdrawal.

Sources: the 2026 Form 8606 and its instructions, IRS Publications 590-A and 590-B, and IRS 2026 limit announcements.

A stack of blank cream paper forms with empty ruled boxes, a fountain pen, reading glasses, and a calculator on a walnut desk, suggesting filling out IRS Form 8606.
Form 8606, Nondeductible IRAs, tracks after-tax basis so the same money is not taxed twice.

What is IRS Form 8606?

Form 8606 is an IRS form with three parts. Taxpayers use it each tax year to report:

  • Nondeductible contributions to traditional IRAs.
  • Traditional IRA distributions when you have basis.
  • Conversions from traditional IRAs to Roth IRAs.
  • Distributions from Roth IRAs.

Your basis is the total of nondeductible amounts you contributed, plus nontaxable amounts rolled in, minus nontaxable distributions. It is your cost basis: after-tax money not taxed again. Deductible contributions and earnings, such as interest and dividends, are taxed when withdrawn.

Who must file Form 8606 for nondeductible IRAs?

The instructions say you generally must file if any of these apply:

  • You made nondeductible IRA contributions to a traditional IRA.
  • You took traditional IRA distributions and your basis is more than zero.
  • You converted any amount to a Roth IRA.
  • You took Roth IRA distributions, other than a rollover, recharacterization, or return of certain contributions.
  • You inherited a traditional IRA with basis, or an inherited Roth IRA paid a nonqualified distribution.

For tax purposes, “traditional IRA” on the form includes traditional SEP and SIMPLE IRAs.

When you don’t need Form 8606

You don’t file Form 8606 just for regular Roth IRA contributions. With no nondeductible contributions ever, report traditional IRA distributions directly on your return.

Do I file Form 8606 with my tax return?

Yes. Attach it to Form 1040, 1040-SR, or 1040-NR, filing by the due date, including extensions. Not filing an income tax return? Sign Form 8606 and mail it alone to the IRS where you would send Form 1040.

Married filing jointly: one form per spouse

When both spouses must file, each files a separate form, even when married filing jointly, because each person tracks basis on their own.

Part I: nondeductible contributions and traditional IRA distributions

Part I is where you report what you contributed and where the taxable portion of distributions is calculated.

A glass jar of coins resting on a blank folded paper slip beside an empty glass jar, a brass paperweight, and a pencil on a light oak desk, suggesting nondeductible IRA contributions.
Nondeductible contributions go on Part I of Form 8606 for the year they are for.

Line 1: what you contributed for the year

Enter nondeductible traditional IRA contributions for the 2026 tax year, including money contributed from January 1 through April 15, 2027, for 2026. You can’t deduct the line 1 amount. The 2026 tax-year limit is $7,500, or $8,600 at 50 or older, across all traditional and Roth IRAs.

Lines 2 and 3: your basis so far

Line 2 is your basis from earlier tax years, generally line 14 of your last Form 8606. Line 3 adds what you contributed this year. With no distribution or conversion this year, line 3 becomes the basis amount on line 14 and you stop.

Lines 6 to 13: the pro-rata calculation

If you took a distribution or converted, line 6 asks for the year-end value of every traditional, SEP, or SIMPLE IRA account, plus outstanding rollovers.

Line 9 adds that value, the year’s distributions, and conversions in aggregate. Line 10 divides your basis on line 5 by that total amount. The non-taxable portion of a conversion (line 11) and of other distributions (line 12) is determined by that ratio. This is the pro-rata rule: you can’t convert only after-tax dollars while pre-tax IRA money exists.

Lines 14 and 15: carry-forward basis and Form 1040

Line 14 is your basis left for future tax years. Line 15c is the taxable amount of traditional IRA distributions you didn’t convert, calculated after basis, and goes on Form 1040 line 4b. It may also be subject to the 10% additional tax penalty if you were under 59½, unless one of the exceptions applies.

Why people contribute money without a deduction

Most nondeductible contributions happen because income limits stop you from being able to deduct them. If you or your spouse is covered by a workplace retirement plan, the 2026 deduction phases out at these income levels, by filing status:

  • Single and covered by an employer plan: $81,000 to $91,000.
  • Married filing jointly, contributing spouse covered: $129,000 to $149,000.
  • Not covered, but married to someone who is: $242,000 to $252,000.
  • Married filing separately and covered: $0 to $10,000.

Above the range, you can still contribute money with no deduction; it is treated as nondeductible. You can also choose not to deduct an eligible contribution.

Part II: reporting a Roth conversion

Part II reports conversions from traditional, SEP, or SIMPLE IRAs. Line 16 is the net amount you converted, line 17 is your basis in it, and line 18 is the taxable portion, added to income on Form 1040 line 4b.

If you completed Part I, line 17 is determined on line 11, so the pro-rata math carries into Part II. Conversions made in 2018 or later can’t be recharacterized, so the reported conversion stands, along with its income tax.

Two plain kraft envelopes on a dark desk with a line of coins running from the flat left envelope to the fuller right envelope, suggesting a traditional IRA to Roth IRA conversion.
Part II of Form 8606 figures the taxable amount of a Roth conversion.

Form 8606 and the backdoor Roth

A backdoor Roth means two entries in one year: the contribution on line 1 and the conversion in Part II. With no other traditional, SEP, or SIMPLE IRA money at year-end, little of a backdoor Roth is taxable. Otherwise, lines 6 to 13 make part of it taxable. Our backdoor Roth IRA guide covers the strategy; this page covers the paperwork. A mega backdoor Roth rolled into a Roth IRA also needs basis records.

Part III: Roth IRA distributions

Part III figures the taxable part of nonqualified Roth IRA distributions. Line 19 totals those transactions; qualified distributions generally stay off it. Line 22 is your basis in regular Roth contributions, which come out first and tax free, before earnings.

Line 24 is your basis in conversions and rollovers. Any portion left on line 25c is taxable, and line 23 amounts may be subject to the 10% additional tax on Form 5329. Early retirees on a Roth conversion ladder rely on these lines.

Tracking IRA basis over the years

Each year’s return builds on the last. Your basis amount carries from line 14 to next year’s line 2, so one missing year breaks the chain.

An open accordion file holding blank papers with blank index cards and a brass binder clip on a dark desk, suggesting keeping IRA basis records for Form 8606.
Keep every Form 8606 and Form 5498 until all your IRA money is distributed.

Records to keep

Keep these until all IRA money is distributed:

  • Page 1 of Form 1040 for each year you contributed without a deduction.
  • Every Form 8606 with its statements and worksheets.
  • Forms 5498 showing contributions and year-end values.
  • Forms 1099-R for each year with a withdrawal.

Is Form 5498 the same as Form 8606?

No. Your IRA trustee sends Form 5498 to report contributions and account values. You file Form 8606 to report basis, using those figures.

What is the penalty for not filing Form 8606?

If you must file Form 8606 to report a nondeductible contribution and don’t, the tax penalty is $50 unless you show reasonable cause. Overstating nondeductible contributions brings a $100 tax penalty. The bigger cost is lost basis: paying tax twice on money you already paid tax on.

Fixing a missing or wrong form

You can generally switch a contribution from nondeductible to deductible, or back, within the Form 1040-X filing window, attaching a corrected Form 8606.

Does TurboTax file Form 8606?

Tax software or a tax preparer can produce Form 8606, a federal tax form attached to your return. Before filing, confirm it is included.

SEP and SIMPLE IRAs on the form

Employer contributions to SEP IRAs and SIMPLE IRAs are not nondeductible contributions, so they stay off line 1. But SEP IRA and SIMPLE IRA balances, earnings and interest included, count in the line 6 total, so a large SEP IRA can make a conversion mostly taxable. Taxpayers who convert should total every one of those IRAs first. A 401(k) or other employer plan account is not part of line 6.

A sealed plain white envelope leaning on a closed laptop beside a mug of tea and a pencil on a sunlit desk, suggesting filing Form 8606 with a tax return.
File Form 8606 with your Form 1040, or by itself if you have no return to file.

Common Form 8606 mistakes people miss

  • Late filing or no filing, so basis is never recorded.
  • Leaving SEP or SIMPLE IRAs out of line 6.
  • Reporting a backdoor Roth conversion as fully taxable despite basis.
  • Filing one form for both spouses.
  • Claiming a deduction for an amount also reported on line 1.
  • Skipping Form 8606 to report distributions from a Roth IRA before 59½.

Related guides

For the rules behind conversions, see our Roth conversion and traditional IRA guides, and this year’s IRA contribution limits. Our Roth IRA guide covers withdrawals, and retirement tax strategy covers the bigger picture.

The bottom line

Form 8606 proves which IRA money was already taxed. File it each year you make nondeductible contributions, convert, or take nonqualified Roth distributions, and keep every copy.

Written by Tim Schmidt and reviewed for tax and account accuracy by Sean Webster, CPA. Last reviewed November 10, 2026 (America/New_York). This guide is for general education, not tax, legal, or investment advice, and not a recommendation to contribute or convert. IRAInvesting.com is not a custodian, broker-dealer, tax preparer, or investment adviser. Talk with a licensed tax professional before you act, and confirm current limits on IRS.gov. Investing involves risk, including possible loss of principal.