The backdoor Roth is two simple steps — nondeductible contribution, then conversion. The pro-rata rule across all your IRAs is where it goes wrong. Worked example inside.
If your income is too high to contribute to a Roth IRA directly, you can still get money in through the backdoor: contribute to a traditional IRA (nondeductible — no income limit applies to that), then convert the traditional IRA to Roth. Done cleanly, the conversion is nearly tax-free, because you're converting money that was never deducted. For 2026, that's up to $7,500 moved into permanently tax-free growth, every year, at any income.
The words "done cleanly" carry all the weight. One rule — the pro-rata rule — determines whether your conversion is tax-free or mostly taxable, and it looks at IRA balances most people forget they have. This post walks the steps in order, works the pro-rata math with real numbers, and covers the fix if you're currently blocked. It expands on move #1 from our pillar on the best tax planning moves for high-income W-2 employees.
Direct Roth IRA contributions phase out above income limits that most tech and professional couples blow past. But two other doors have no income limit at all: making a nondeductible contribution to a traditional IRA, and converting a traditional IRA to a Roth. Chain them together and you've replicated a Roth contribution at any income. This isn't a gray area — the two steps are each explicitly allowed, the combination has been openly used and reported for years, and Congress has repeatedly declined to close it. Old worries about the step-transaction doctrine are settled practice at this point; the backdoor Roth is a routine planning move, not an aggressive position.
That's the whole procedure. Married couples can run it twice — each spouse has their own limit and their own IRAs.
Why bother for $7,500 a year? Because it compounds in the one account type the IRS never touches again: no tax on growth, no tax on qualified withdrawals, no required minimum distributions during your lifetime. Run annually for a couple across a couple of decades of high-earning years, the backdoor alone builds a six-figure tax-free bucket — the most valuable dollars in a retirement plan, because they come out clean at whatever future tax rates turn out to be.
Here's the rule: when you convert money from a traditional IRA, you can't choose to convert just the after-tax dollars. The IRS treats all of your traditional, SEP, and SIMPLE IRAs — across every custodian — as one big pot, and every conversion carries out pre-tax and after-tax money in proportion to the whole pot. The snapshot is taken on December 31 of the conversion year, not the day you convert.
Worked example. You contribute $7,500 nondeductible and convert it — but you also have a $67,500 rollover IRA from an old 401(k), all pre-tax. Your total IRA pot is $75,000, of which $7,500 (10%) is after-tax basis.
So the "tax-free" backdoor became a mostly-taxable conversion — not a penalty, but real tax you didn't plan for, and exactly the outcome the maneuver was supposed to avoid. Note what doesn't count in the pot: 401(k) and other workplace plan balances, inherited IRAs, and your spouse's IRAs. The pro-rata calculation is per-person, IRAs only.
If pre-tax IRA money is blocking you, the standard fix is a reverse rollover: move the pre-tax IRA balance into your current employer's 401(k), if the plan accepts roll-ins (most large-employer plans do). Workplace plans aren't part of the pro-rata pot, so once the IRA holds only your fresh nondeductible contribution, the conversion is clean. Sequence matters: get the rollover completed before December 31 of the year you convert, since that's when the pro-rata snapshot is taken. Solo 401(k)s work for this too if you have self-employment income and the plan document allows roll-ins.
Alternatively, small pre-tax balances can simply be converted along with the contribution — pay the tax once, clear the deck, and every future year is clean. For a $10,000 rollover IRA that's often worth it; for $500,000, it usually isn't.
The backdoor Roth is the entry-level move at $7,500 a year. If your employer's 401(k) allows after-tax contributions with in-plan conversions or in-service rollovers, the mega backdoor Roth runs the same logic at several times the scale inside the plan, where the pro-rata rule doesn't reach your IRAs at all. Alongside it, an HSA is the other no-brainer shelter for high earners — triple tax-advantaged if you use it right. And Roth capacity now has one more inbound route worth knowing: leftover education money can move via 529-to-Roth rollovers — lifetime cap of $35,000, subject to the annual IRA limits and a 15-year account age requirement.
The backdoor Roth is two transactions and one form. The pro-rata rule is the only real trap — and it's checked on December 31, so clear out pre-tax IRA money before year-end.
For 2026, the playbook is: confirm your traditional/SEP/SIMPLE IRA balances are zero (or roll them into your 401(k) before December 31), contribute $7,500 nondeductible, convert promptly, and file Form 8606. Repeat annually, per spouse. The mistakes are all avoidable — a forgotten rollover IRA, a missed 8606, a conversion left to grow for months. Taxagon's CPAs and EAs set up and paper backdoor Roths for high-income clients every year, including cleaning up past years' missing forms — if you want it done right as part of a broader plan, reach out.
This article is general information, not tax advice for your specific situation. Tax law changes; figures are for the years stated.
Talk it through with a licensed US tax professional — we'll tell you honestly whether it applies to your situation.
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