The "backdoor Roth" is a two-step technique that lets people whose income is above the direct Roth IRA contribution limits still get money into a Roth — this article walks through how it works, the pro-rata rule that determines how much of the conversion is taxable, and the most common ways the strategy goes wrong.

A direct Roth IRA contribution requires that your modified adjusted gross income (MAGI) fall within the IRS's annual phase-out range. Above the upper end of that range, you cannot contribute directly to a Roth IRA. See "Roth IRA — overview and eligibility" for how the MAGI rules work.

The backdoor Roth is a two-step workaround that uses two existing IRS rules in combination:

Combine those two rules — make a non-deductible contribution to a Traditional IRA, then convert that balance to a Roth IRA — and the result is functionally a Roth contribution made by someone whose income would otherwise have disqualified them. That's the strategy.

The mechanics are straightforward; the pitfalls — especially the pro-rata rule — are not. We recommend consulting a tax advisor or attorney for guidance specific to your situation before executing this strategy.

The strategy plays out in this order:

If the only money in your Traditional IRA is the non-deductible contribution you just made — and there is no investment growth between the contribution and the conversion — the conversion is essentially tax-free, because the entire converted amount is basis. In practice, this clean outcome only happens when the pro-rata rule does not apply (see below).

Internal Revenue Code (IRC) Section 408(d)(2) defines the pro-rata rule for IRA distributions and conversions. The rule says that when you take any distribution or conversion from a Traditional IRA, the IRS treats your entire pre-tax + after-tax basis across all of your Traditional, SEP, and SIMPLE IRAs combined as a single pool. You cannot pull only the after-tax portion.

In practical terms, consider this scenario. You make a $7,000 non-deductible contribution to a Traditional IRA. You also have $93,000 of pre-tax money sitting in another Traditional IRA (or SEP, or SIMPLE IRA). Your total IRA balance is $100,000 — of which $7,000 (7%) is basis and $93,000 (93%) is pre-tax.

If you convert $7,000 to a Roth, only 7% of that conversion is treated as basis (tax-free). The other 93% is taxable as ordinary income.

This is the trap. People who already have meaningful pre-tax balances in Traditional, SEP, or SIMPLE IRAs typically cannot use the backdoor Roth cleanly without a much larger tax bill than they expected.

A few details that matter:

There is a commonly used workaround for the pro-rata trap: roll the pre-tax Traditional / SEP / SIMPLE IRA balance into an employer 401(k) before the end of the conversion year. Employer plan balances are not counted in the pro-rata calculation. Once those pre-tax dollars are inside a 401(k), the only money left in your Traditional IRA at year-end is the non-deductible contribution, and the conversion is clean.

This only works if (a) your employer's 401(k) accepts incoming rollovers from IRAs, and (b) the timing lines up — the pro-rata calculation uses the December 31 balance, so the rollover has to be completed by then.

This workaround has its own considerations (employer plan investment menu, plan-level fees, future access). We recommend consulting a tax advisor or attorney for guidance specific to your situation.

The basis tracking on Form 8606 is what makes the backdoor Roth defensible to the IRS. Skipping or mis-filing Form 8606 is a frequent mistake that turns a properly executed strategy into a tax mess. File Form 8606 in:

Missing a year of Form 8606 is correctable but is paperwork you do not want to deal with. Track basis carefully, year over year.

In the years immediately after the backdoor Roth became popular, there was IRS commentary about whether the contribution + conversion should be collapsed under the step-transaction doctrine and treated as a direct (and impermissible) Roth contribution. Congressional report language accompanying the Tax Cuts and Jobs Act of 2017 essentially confirmed that the technique is permitted, and the IRS has not challenged it as a step transaction in current practice. The strategy is widely used today, but as with any tax-positioning technique, the law can change. We recommend consulting a tax advisor or attorney for guidance specific to your situation.

The mega backdoor Roth is a separate, employer-plan-based technique that is often confused with the standard backdoor Roth. It uses after-tax contributions to a 401(k) plan above the standard employee deferral limit, followed by either an in-plan Roth conversion or an in-service rollover to a Roth IRA. The mega backdoor Roth depends on specific plan features that not all employer plans offer, and the dollar amounts involved are substantially larger.

The mega backdoor Roth is outside the scope of this article. If your employer plan supports it and you are considering using it, we recommend consulting a tax advisor or attorney for guidance specific to your situation.

If I have a SEP IRA or SIMPLE IRA at a different custodian, does that count against the pro-rata rule?
Yes. The pro-rata rule aggregates all of your Traditional, SEP, and SIMPLE IRAs across all custodians. The IRS does not look at any single account in isolation.

I'm above the Roth direct-contribution MAGI limit. Can I still contribute to a Traditional IRA?
Yes, in terms of the contribution itself. There is no income limit on Traditional IRA contributions. Whether the contribution is deductible phases out at high incomes when you or your spouse is covered by a workplace retirement plan — but a non-deductible contribution is always permitted, and that is the contribution the backdoor Roth strategy uses.

Does the backdoor Roth use up my annual IRA contribution limit?
Yes. The non-deductible Traditional IRA contribution counts toward the annual IRA contribution limit, which is shared across Traditional and Roth IRAs combined — see "Contributions — limits, deadlines, and how to make them". The conversion step does not have its own limit.

Is there a five-year clock on the converted amount?
Yes. Each Roth conversion — including a backdoor Roth conversion — starts its own five-year clock. Withdrawing the converted amount within five years of the conversion can re-trigger the 10% additional tax if you are under 59½. See "Roth conversions — how they work" for the conversion five-year rule mechanics.

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