A nondeductible traditional IRA contribution is money paid into a traditional IRA that the taxpayer does not deduct under section 219. The Code permits it in one sentence: subject to the provisions of that subsection, designated nondeductible contributions may be made on behalf of an individual to an individual retirement plan (26 U.S.C. 408(o)(1)). The contribution buys no deduction. What it buys is basis, and basis is only worth anything if it is reported.
The IRS states the practitioner’s version of the same thing: although the deduction for IRA contributions may be reduced or eliminated, contributions can be made to the IRA up to the general limit or, if it applies, the Kay Bailey Hutchison Spousal IRA limit, and the difference between total permitted contributions and the IRA deduction, if any, is the nondeductible contribution (IRS, Publication 590-A (2025)).
What the Code Actually Calls It
The statute’s term is designated nondeductible contribution, and the word designated is doing real work.
For purposes of that paragraph, the term means any contribution to an individual retirement plan for the taxable year which is designated, in such manner as the Secretary may prescribe, as a contribution for which a deduction is not allowable under section 219 (26 U.S.C. 408(o)(2)(C)(i)). The opening scope words matter, because the definition is written for that paragraph rather than for the Code at large.
The designation is not a decision made at the bank. Any designation under that clause shall be made on the return of tax imposed by chapter 1 for the taxable year (26 U.S.C. 408(o)(2)(C)(ii)). A contribution becomes nondeductible on the return, not in the account.
How Much Can Be Designated
The amount of the designated nondeductible contributions made on behalf of any individual for any taxable year shall not exceed the nondeductible limit for that year (26 U.S.C. 408(o)(2)(A)).
That limit has two limbs and it is a subtraction. The nondeductible limit means the excess of the amount allowable as a deduction under section 219 determined without regard to section 219(g), over the amount allowable as a deduction under section 219 determined with regard to section 219(g) (26 U.S.C. 408(o)(2)(B)(i)). In plain terms it is the part of the contribution ceiling that the active-participant phase-out took away.
There is also an election. If a taxpayer elects not to deduct an amount which, without regard to that clause, is allowable as a deduction under section 219 for any taxable year, the nondeductible limit for that year shall be increased by that amount (26 U.S.C. 408(o)(2)(B)(ii)). The IRS says the same from the filing side: when you file, you can even designate otherwise deductible contributions as nondeductible contributions (IRS, Publication 590-A (2025)).
Why the Deduction Gets Taken Away in the First Place
If, for any part of any plan year ending with or within a taxable year, an individual or the individual’s spouse is an active participant, each of the dollar limitations contained in subsections (b)(1)(A) and (c)(1)(A) for that taxable year shall be reduced, but not below zero, by the amount determined under paragraph (2) (26 U.S.C. 219(g)(1)).
The reduction is proportional. It bears the same ratio to the dollar limitation as the excess of adjusted gross income over the applicable dollar amount bears to $10,000, or $20,000 in the case of a joint return (26 U.S.C. 219(g)(2)(A)).
One proviso inside that computation is easy to lose. No dollar limitation shall be reduced below $200 under paragraph (1) unless, without regard to that subparagraph, the limitation is reduced to zero (26 U.S.C. 219(g)(2)(B)). So a taxpayer partway through the range does not grind down to a token deduction; the floor is $200 until the phase-out closes it entirely (26 U.S.C. 219(g)(2)(B)).
The applicable dollar amount in the statute is $80,000 for a taxpayer filing a joint return, $50,000 for any other taxpayer other than a married individual filing separately, and zero for a married individual filing a separate return (26 U.S.C. 219(g)(3)(B)). Those are base figures, not this year’s. Each of the dollar amounts in paragraphs (3)(B)(i), (3)(B)(ii) and (7)(A) is increased by a cost-of-living adjustment determined under section 1(f)(3) for taxable years beginning in a calendar year after 2006 (26 U.S.C. 219(g)(8)).
The indexed figures are the ones a return runs on. For 2025, a taxpayer covered by an employer plan phases out between a modified AGI over $79,000 and $89,000 filing single or head of household, and between $126,000 and $146,000 filing jointly or as a qualifying surviving spouse (IRS, Publication 590-A (2025)). A covered married individual filing separately phases out between $0 and $10,000 (IRS, Publication 590-A (2025)). A taxpayer who is not covered but whose spouse is phases out between $236,000 and $246,000 on a joint return, and between $0 and $10,000 filing separately (IRS, Publication 590-A (2025)). The AGI used is a modified one, computed the way modified adjusted gross income sets out for this deduction.
Two side rules travel with the phase-out. Where the taxpayer is caught solely because a spouse is an active participant, the applicable dollar amount under paragraph (3)(B)(i) is $150,000 and the amount under paragraph (2)(A)(ii) is $10,000, applied to that individual but not to the spouse (26 U.S.C. 219(g)(7)). And a husband and wife who file separate returns for a taxable year and live apart at all times during that year are not treated as married individuals for purposes of that subsection (26 U.S.C. 219(g)(4)). Both limbs of that second rule have to hold.
Form 8606 Is Not Optional
To designate contributions as nondeductible, you must file Form 8606, and you must file it to report nondeductible contributions even if you do not have to file a tax return for the year (IRS, Publication 590-A (2025)). One situation is carved out of that. A Form 8606 is not used for the year you make a rollover from a qualified retirement plan to a traditional IRA where the rollover includes nontaxable amounts, and in those situations the form is completed for the year you take a distribution from that IRA (IRS, Publication 590-A (2025)).
The statute puts the reporting duty on two separate triggers, not one. Any individual who makes a designated nondeductible contribution to any individual retirement plan for any taxable year, or receives any amount from any individual retirement plan for any taxable year, shall include on the return of tax imposed by chapter 1 for that year and any succeeding taxable year the information described in the next subparagraph (26 U.S.C. 408(o)(4)(A)). The second trigger catches taxpayers who stopped contributing years ago and simply took a distribution.
The information required is a short list: the amount of designated nondeductible contributions for the year, the amount of distributions from individual retirement plans for the year, the excess, if any, of aggregate designated nondeductible contributions for all preceding years over the aggregate distributions from individual retirement plans that were excludable from gross income for those years, the aggregate balance of all the individual’s individual retirement plans as of the close of the calendar year in which the taxable year begins, and such other information as the Secretary may prescribe (26 U.S.C. 408(o)(4)(B)).
What Happens When Nobody Files It
The consequence is not a lost form. It is a lost basis.
If you do not report nondeductible contributions, all of the contributions to your traditional IRA will be treated like deductible contributions when withdrawn, and all distributions from your IRA will be taxed unless you can show, with satisfactory evidence, that nondeductible contributions were made (IRS, Publication 590-A (2025)). That is the same money taxed on the way in and again on the way out.
Two penalties sit behind the requirement. The contribution rules themselves point at only one of them, for penalty where an individual reports designated nondeductible contributions not made (26 U.S.C. 408(o)(4)(C)); the second is found by reading the penalty section itself. An individual required to furnish information under section 408(o)(4) who overstates the amount of designated nondeductible contributions made for a taxable year pays a penalty of $100 for each such overstatement, unless it is shown that the overstatement is due to reasonable cause (26 U.S.C. 6693(b)(1)). An individual who fails to file a form required under section 408(o)(4) pays a penalty of $50 for each such failure, unless the failure is shown to be due to reasonable cause (26 U.S.C. 6693(b)(2)). The IRS states both figures the same way (IRS, Publication 590-A (2025)).
The Basis, and Why It Cannot Be Withdrawn on Its Own
You have a cost basis in a traditional IRA if you made any nondeductible contributions, and that cost basis is the sum of the nondeductible contributions to the IRA minus any withdrawals or distributions of nondeductible contributions (IRS, Publication 590-A (2025)).
Getting it back out is where most of the confusion lives. Except as otherwise provided in that subsection, any amount paid or distributed out of an individual retirement plan is included in gross income by the payee or distributee in the manner provided under section 72 (26 U.S.C. 408(d)(1)). Then three aggregation rules bite. For purposes of applying section 72, all individual retirement plans shall be treated as 1 contract, all distributions during any taxable year shall be treated as 1 distribution, and the value of the contract, the income on the contract and the investment in the contract shall be computed as of the close of the calendar year in which the taxable year begins (26 U.S.C. 408(d)(2)). A closing sentence adds that for purposes of the third rule, the value of the contract shall be increased by the amount of any distributions during the calendar year (26 U.S.C. 408(d)(2)).
All three limbs point the same way. A taxpayer cannot open a separate account, fill it with nondeductible money, and empty that one tax free, because every traditional IRA the person holds is one contract for this purpose (26 U.S.C. 408(d)(2)). The IRS says the practical result plainly: distributions from traditional IRAs will commonly include both taxable and nontaxable, that is cost basis, amounts (IRS, Publication 590-A (2025)).
Earnings are a separate matter from basis. As long as contributions are within the contribution limits, none of the earnings or gains on contributions, deductible or nondeductible, will be taxed until they are distributed (IRS, Publication 590-A (2025)). So the basis comes back tax free and the growth on it does not. This is a different mechanism from the employer-plan after-tax contributions governed by Publication 575, where the ratio can turn on whether the plan treats employee money as a separate contract.
Two Amounts That Are Nondeductible for a Different Reason
Not every nondeductible contribution comes from a phase-out.
Nondeductible contributions may include repayments of qualified reservist distributions (IRS, Publication 590-A (2025)).
And for contributions after December 20, 2019, a taxpayer may elect to increase the nondeductible IRA contribution limit by some or all of the amount of difficulty of care payments received, which are a type of qualified foster care payment, though not above the $7,000 IRA deductible amount, or $8,000 for someone age 50 or older (IRS, Publication 590-A (2025)). The increase equals the lesser of the amount of difficulty of care payments excluded from gross income, or the amount by which the deductible limit for IRA contributions exceeds the taxpayer’s compensation included in gross income for the year (IRS, Publication 590-A (2025)). The statute states it as a conditional election. Where the deductible amount in effect for the taxable year under section 219(b) exceeds the compensation includible in the individual’s gross income for that year, the individual may elect to increase the nondeductible limit under paragraph (2) by an amount equal to the lesser of that excess or the amount so excluded (26 U.S.C. 408(o)(5)).
Common Questions
The sources settle what it does, not whether it suits a particular taxpayer. What they establish is that the contribution creates cost basis recoverable tax free later (IRS, Publication 590-A (2025)), that the earnings on it stay untaxed until distributed (IRS, Publication 590-A (2025)), and that the basis is only recognised if Form 8606 was filed (IRS, Publication 590-A (2025)). Everything past that turns on the taxpayer’s own facts.
The publication does not set out a late-filing procedure. What it does say is that the designation is made on the return for the taxable year (26 U.S.C. 408(o)(2)(C)(ii)), that the form must be filed even where no return is otherwise required (IRS, Publication 590-A (2025)), and that the failure-to-file penalty is excused where the failure is shown to be due to reasonable cause (26 U.S.C. 6693(b)(2)).
No provision above makes it do so. The basis changes how much of a distribution is taxable, through section 72 and the aggregation rules (26 U.S.C. 408(d)(2)). How much has to come out is settled separately, under the rules covered in required minimum distribution.
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