The "backdoor Roth IRA": what the term means

The phrase "backdoor Roth IRA" appears often in personal finance writing, and it can sound like a product. It is not one. It is a nickname for a sequence of two ordinary transactions that, together, let a person whose income is too high for a direct Roth IRA contribution end up with money in a Roth IRA. This article explains what the steps are, why the tax result is frequently misunderstood, and what gets reported.

Why the idea exists

Direct contributions to a Roth IRA are limited by income. For 2026, the IRS says the ability to contribute phases out between $153,000 and $168,000 of modified adjusted gross income for single filers and between $242,000 and $252,000 for married couples filing jointly. Above the range, no direct contribution is allowed.

Two other rules have no such income ceiling:

• Anyone with compensation can contribute to a traditional IRA. High income may prevent a deduction, but IRS Publication 590-A explains that the contribution can still be made as a nondeductible one.
• Converting a traditional IRA to a Roth IRA is not restricted by income.

Put those together and the "backdoor" is simply: contribute to a traditional IRA without taking a deduction, then convert that money to a Roth IRA.

The two steps

1. Nondeductible contribution. The person contributes to a traditional IRA, up to the annual limit, and does not deduct it. The contribution creates what the IRS calls basis: money that has already been taxed.
2. Conversion. The person converts the traditional IRA balance to a Roth IRA. The mechanics are the same as any other conversion, described in Roth conversions explained.

If the only money in any of the person's traditional IRAs is the new after-tax contribution, the conversion is mostly a return of basis, and only any earnings that built up between the two steps are taxable. That clean result is the version usually described. It does not hold for everyone.

The pro-rata rule

The tax law does not let a person choose to convert only the after-tax dollars. IRS Publication 590-B explains that when a traditional IRA contains nondeductible contributions, distributions consist partly of basis and partly of deductible contributions and earnings, and until all of the basis has been distributed, each distribution is partly nontaxable and partly taxable.

Two features of this calculation matter most:

• All IRAs are counted together. The computation on Form 8606 uses the combined value of all of a person's traditional IRAs, including SEP and SIMPLE IRAs, not just the account that received the new contribution. Opening a separate account for the nondeductible money does not isolate it.
• The measurement uses year-end values. The form looks at total balances as of December 31 of the year of the conversion, so a rollover into an IRA later in the same year can change the result.

Balances in a workplace plan such as a 401(k) are not IRAs and are not part of the Form 8606 calculation. A spouse's IRAs are not counted either, because IRAs are owned individually.

A hypothetical example

Suppose someone has $92,500 in a traditional IRA that came from an old 401(k) rollover, all of it pre-tax. In 2026 they make a $7,500 nondeductible contribution and then convert $7,500 to a Roth IRA. Assume no investment gains or losses, for simplicity.

• Total traditional IRA money: $100,000
• After-tax basis: $7,500, which is 7.5% of the total
• Tax-free part of the $7,500 conversion: 7.5%, or $562.50
• Taxable part: $6,937.50

The person expected a tax-free conversion and instead has close to $7,000 of additional taxable income. The remaining basis is not lost. It stays on record through Form 8606 and is recovered gradually with later distributions or conversions. These numbers are illustrative only.

Paperwork

The IRS says Form 8606 is used to report nondeductible contributions to traditional IRAs, distributions from traditional, SEP or SIMPLE IRAs when a person has ever made nondeductible contributions, and conversions to Roth IRAs. In a backdoor arrangement the form does two jobs: it records the basis created by the contribution and it computes the taxable portion of the conversion.

Skipping the form is a common source of trouble. Without it there is no record of basis, and the full conversion can look taxable. The IRA custodian will also issue Form 1099-R for the conversion, which reports the gross amount and does not by itself show how much is taxable.

Things that are easy to overlook

• Existing pre-tax IRAs. Rollover IRAs, SEP IRAs and SIMPLE IRAs all enter the pro-rata math. Some workplace plans accept roll-ins of pre-tax IRA money, which is one way people reduce their IRA balances before year-end; whether a plan allows this depends on the plan. See rolling an old 401(k) into a new employer's plan for how plan roll-ins work in general.
• Earnings between the steps. Any growth before the conversion is taxable when converted.
• The five-year period on conversions. A person under 59½ who withdraws converted amounts within five years may owe the 10% additional tax on the portion that was taxable at conversion. See the Roth IRA five-year rules.
• The contribution limit still applies. The nondeductible contribution counts against the regular annual IRA limit covered in IRA contribution limits and income rules.
• Rules can change. The arrangement rests on current law. Congress sets the rules for contributions and conversions and can revise them.

Whether the backdoor approach produces the result a person expects comes down to the facts: what other IRA balances exist on December 31, how the forms are completed, and how the Roth money will later be used.