The backdoor Roth IRA: a perfectly legal side entrance with a very specific doormat

By Tom, CPA · Updated October 25, 2026

TL;DR: High earners above the 2026 Roth IRA income limits ($153,000–$168,000 single, $242,000–$252,000 joint) can often still fund a Roth by making a nondeductible traditional IRA contribution and converting it. The plan works cleanly only if you have no other pre-tax IRA money, because of the pro-rata rule.

Educational only, not tax, legal, or investment advice. Examples are illustrations, not predictions. Rules and limits change; verify current figures and talk to a qualified professional about your situation.

Congress decided that people above certain incomes can't contribute directly to a Roth IRA. Congress also decided, separately, that anyone can contribute to a traditional IRA (deductible or not), and that anyone can convert a traditional IRA to a Roth. Put those two decisions next to each other and you have the "backdoor Roth," a strategy so widely used that it appears in tax software menus with its own little wizard.

It's legal, common and simple. It's also surprisingly easy to botch, mostly because of one rule that hides in Form 8606 like a raccoon in the attic. Let's walk through it.

CPA Warning Label: The backdoor Roth is two easy steps and one invisible trap: any pre-tax IRA balance on December 31 makes part of your conversion taxable. Check every IRA, SEP and SIMPLE first.

Who needs the backdoor

For 2026, the IRS says the Roth IRA contribution phase-out range is:

Above the top of your range, direct Roth contributions aren't allowed. The 2026 IRA contribution limit is $7,500, plus a $1,100 catch-up if you're 50 or older, and you need at least that much taxable compensation (or a working spouse, via a spousal IRA).

The two steps

1. Contribute to a traditional IRA and don't deduct it. If you or your spouse are covered by a workplace plan and your income is above the deduction phase-out, the contribution is nondeductible anyway. You report it on Form 8606, which creates "basis" (after-tax money) in your IRAs.
2. Convert the traditional IRA to a Roth IRA. Conversions have no income limit. Because the contribution was already taxed, converting it creates little or no taxable income, as long as you have no other pre-tax IRA money (more on that in a moment).

Any earnings between step 1 and step 2 are taxable when converted. Many people convert soon after contributing so there's little to tax. Some keep the cash in a money market fund until the conversion. The IRS has no specific waiting period rule for this, though some people choose to wait anyway out of caution.

The pro-rata trap

When you convert, the IRS doesn't let you choose which dollars move. It looks at all your traditional, SEP and SIMPLE IRAs together and treats the conversion as a proportional slice of pre-tax and after-tax money. The calculation uses your total IRA value at December 31 of the year of the conversion, not the day you convert.

Illustration (assumptions): Larry makes a $7,500 nondeductible contribution and converts $7,500 in March. He forgot he has a $92,500 rollover IRA from an old job (all pre-tax). On December 31, his IRAs total $92,500 plus the basis, so after-tax money is $7,500 of $100,000, or 7.5%.

• Tax-free part of the $7,500 conversion: 7.5% = $562.50
• Taxable part: $6,937.50

His "tax-free" backdoor became mostly taxable. The detailed math is in our pro-rata rule guide, and the pro-rata calculator runs it for you.

The common fix is to roll the pre-tax IRA money into a current employer 401(k) that accepts roll-ins, before December 31. 401(k) balances are not part of the pro-rata calculation. Solo 401(k)s can work for the self-employed, too.

Form 8606 and reporting

Form 8606 does the heavy lifting. Part I records the nondeductible contribution and computes the taxable portion of conversions using the pro-rata formula. Part II reports the conversion itself. Your IRA custodian will send a Form 1099-R for the conversion and a Form 5498 for the contribution. The 5498 often shows up after you file, which confuses everyone. That's normal.

Missing Form 8606 is a classic error. IRS Publication 590-A notes a $50 penalty for failing to file Form 8606 when required (unless you can show reasonable cause), but the bigger problem is losing track of your basis and paying tax twice later.

Timing and the five-year clock

Each conversion starts its own five-year clock for the 10% additional tax if you're under 59½, and the account's first Roth contribution or conversion starts the clock for qualified (tax-free) earnings. Details are in the Roth five-year rules guide. For backdoor contributions, the taxable part of the conversion is usually zero, so the penalty clock rarely bites, but it's good to know it exists.

You can make a prior-year IRA contribution up to the tax filing deadline (generally April 15). Some people make a 2026 contribution in early 2027 and convert it then. That's fine, but the conversion is reported in the year it happens, and the pro-rata math uses that year's December 31 balance.

Common mistakes, ranked by how often they show up

1. Forgetting an old rollover IRA. The pro-rata rule sees every traditional, SEP and SIMPLE IRA you own on December 31, including the one you opened in 2011 and forgot about. A quick inventory of every custodian you've ever used saves a lot of grief.
2. Deducting the contribution by accident. Tax software sometimes assumes a traditional IRA contribution is deductible. If you aren't eligible, or don't want the deduction, the return needs to show it as nondeductible on Form 8606.
3. Contributing directly to the Roth first, then realizing income is too high. An excess Roth contribution can be recharacterized as a traditional IRA contribution (generally by the tax deadline, including extensions), which can then be converted. It's fixable, but it adds paperwork.
4. Opening a SEP IRA in the same year. Self-employed folks who start a SEP IRA add pre-tax IRA money to the December 31 total. A solo 401(k) avoids that problem because 401(k) balances aren't counted.
5. Losing the paper trail. Basis is only as good as your records. Keep every Form 8606 and the matching 1099-R and 5498 forms.

Illustration: a clean backdoor, start to finish

Illustration (assumptions): Fran is 41, single, with modified AGI of $190,000 in 2026, above the $168,000 top of the single phase-out. She has a 401(k) at work and no IRAs at all.

• February: she contributes $7,500 to a new traditional IRA and keeps it in a money market fund. Because she's covered by a workplace plan and her income is well above the $81,000–$91,000 single deduction phase-out, it's nondeductible anyway.
• Late February: the IRA has earned $12. She converts $7,512 to a Roth IRA.
• On her return: Form 8606 shows $7,500 of basis, a $7,512 conversion, and $12 of taxable income. December 31 traditional IRA balance: $0, so the pro-rata math is clean.

Tax cost: income tax on $12. Paperwork cost: one form. Smugness: considerable, but earned.

Is the backdoor worth it every year?

The benefit compounds. A $7,500 Roth contribution that grows for 20 years is, under current law, tax-free on qualified withdrawal, versus a taxable account where dividends and gains are taxed along the way. Over a long career, a decade or two of backdoors adds up to a meaningful tax-free bucket that early retirees can use flexibly, since contributions (and conversions after their five-year clocks) come out first. The trade-off is a little annual admin. For most people above the income limits who have no pre-tax IRA balance, that's a good trade.

A clean backdoor checklist

• Confirm income is above the Roth phase-out (or near it and you'd rather not do the math).
• Check every traditional, rollover, SEP and SIMPLE IRA balance, including your own forgotten ones. A spouse's IRAs don't count toward yours; each spouse runs the pro-rata rule separately.
• If needed, roll pre-tax IRA money into an employer plan first.
• Make the nondeductible contribution, then convert.
• File Form 8606 every year you make a nondeductible contribution or conversion.
• Keep copies of every 8606 forever. Future you will need them.

Workplace plans with after-tax contributions and in-plan conversions can do something similar at a much larger scale. See the mega backdoor Roth guide.