Key takeaways
- Backdoor Roth = anyone over the income limit can do it: nondeductible traditional IRA contribution, then convert. The enemy is the pro-rata rule.
- Mega backdoor Roth = only if your 401(k) allows after-tax contributions plus in-service rollovers. Potentially tens of thousands per year into Roth.
- Both are IRS-acknowledged and legal. Both punish sloppy paperwork — file Form 8606, mind the 5-year clocks.
Trick 1: the regular backdoor Roth
Who it's for: anyone whose income is over the direct Roth IRA limit ($168k single / $252k joint for 2026). There is no income limit on contributing to a traditional IRA, and no income limit on converting to Roth. The backdoor walks through both open doors in sequence.
- 1Contribute after-tax dollars to a traditional IRA. You won't deduct it — it's a nondeductible contribution, up to the $7,500 annual IRA limit.
- 2Convert to Roth. Move it quickly — any growth between contribution and conversion is taxable. Same-day or next-day is the norm.
- 3File Form 8606. This records your after-tax "basis." Without it, the IRS treats the conversion as fully taxable.
The pro-rata surprise. If you hold any pre-tax money in traditional, SEP, or SIMPLE IRAs on December 31, the IRS treats every converted dollar as partly pre-tax — proportionally across all your IRAs. You cannot convert "just the after-tax part." The standard fix: roll pre-tax IRA balances into your current 401(k) first, leaving the IRA empty for a clean backdoor. If you can't move the pre-tax money, the backdoor probably isn't worth it.
Trick 2: the mega backdoor Roth
Who it's for: high savers whose 401(k) plan cooperates. The normal $24,500 elective-deferral limit is only one bucket — the total plan limit for 2026 is $72,000 (employee + employer). Some plans let you fill the gap with after-tax contributions and then roll them into Roth. That's potentially ~$40,000+/year of extra Roth space.
The HR questions that decide everything
"Does our plan allow after-tax (non-Roth) contributions beyond the pre-tax/Roth limit?"
"Does it allow in-service distributions of after-tax money — or in-plan Roth rollovers?"
You need yes to both. After-tax without a rollover path just traps money in a taxable-on-growth bucket — worse than a brokerage account. Most people never ask, so most never know their plan offers it.
5-year clocks. Each mega backdoor rollover starts its own 5-year clock — withdraw the converted dollars before it runs out (and before 59½) and you owe a 10% penalty. Track every rollover's date.
Who should skip both
Skip the backdoor if…
- You hold pre-tax IRA balances you can't roll into a 401(k) — the pro-rata tax will eat the benefit.
- You're under the income limit anyway — just contribute directly and skip the paperwork.
Skip the mega if…
- Your plan fails either HR question — no rollover path, no mega.
- You haven't maxed the HSA, match, and IRA yet — the mega is dessert, not dinner.
What next?
Backdoors move money into the middle tier of the tax pyramid — taxed once, never again. See the full funding order and where the other accounts sit.