A growing number of high-earning Americans are quietly funneling tens of thousands of dollars into Roth accounts each year, well beyond the standard $7,000 IRA limit.
The strategy has an odd name — the mega backdoor Roth — and it's become one of the most talked-about moves in retirement planning.
Most workplace 401(k) plans let you contribute up to $23,000 in 2024, plus a catch-up of $7,500 if you're 50 or older.
But the total cap on all contributions to a 401(k) — including employer matches and after-tax dollars — sits at $69,000 this year.
If your plan allows after-tax contributions and in-service withdrawals or conversions, you can put money in after tax, then convert it to Roth.
The result: earnings grow tax-free, and qualified withdrawals in retirement come out tax-free too.
The catch is that not every employer offers this.
Fidelity, Schwab, and Vanguard all support the mechanics, but your specific plan has to permit after-tax contributions and either in-plan conversions or rollovers to a Roth IRA while you're still working.
A 2023 survey from the Plan Sponsor Council of America found that only about a quarter of 401(k) plans allow after-tax contributions at all.
For those who do have access, the numbers can be striking.
A saver under 50 could potentially move roughly $46,000 into Roth treatment this year, on top of the standard $23,000 deferral — assuming their employer match and plan rules line up.
You pay income tax on the after-tax portion when you convert, so it's not free.
And if you convert earnings rather than just the basis, that portion is taxable too.
Some plans only let you convert the after-tax money itself, which keeps the tax bill smaller.
If you leave the after-tax money sitting in the account for years before converting, the earnings pile up and become taxable at conversion.
Many advisors suggest converting soon after each contribution to limit that.
The strategy also assumes you won't need the money before 59½.
Roth conversions generally require the account to be open five years before earnings come out penalty-free, and each conversion has its own five-year clock for penalty purposes.
That's a detail plenty of people get wrong.
Savers who already max out a traditional 401(k) and a Roth or traditional IRA, have cash left over, and expect to be in a similar or higher tax bracket later.
For someone in a lower bracket now, a plain Roth IRA or regular brokerage account may make more sense.
One more wrinkle: the IRS has been watching.
After-tax contributions that sit unconverted for years can create messy tax reporting.
Keeping records of your basis — the after-tax dollars you put in — is essential when you eventually move the money.
If you're unsure whether your plan supports this, the fastest step is to call your HR benefits line or log into your 401(k) provider and search the summary plan description for "after-tax" and "in-service." It takes about ten minutes and could change your retirement math.
The mega backdoor Roth isn't a magic trick, and it isn't for everyone.
But for a certain slice of American workers, it's one of the few remaining ways to legally shelter a serious chunk of income from future taxes. **Our take:** This strategy rewards people who already have spare cash and a willing employer, which means it widens the gap between savers who can and can't access it.
If your plan doesn't offer it, that's not a failure on your part — it's a plan design choice.
Final Thoughts
The smarter move is to push your HR team to add the feature, because a growing share of workers are asking.