Somewhere in a conference room, an advisor is telling a high earner they can stuff roughly $70,000 a year into Roth savings.
That number is real, but it comes with a maze of plan rules, tax math, and deadlines that the pitch deck tends to skip.
The strategy has a clunky name: the mega backdoor Roth.
It works through your workplace 401(k), not an IRA.
The idea is to contribute after-tax dollars beyond the normal $23,500 employee limit, then convert that money to Roth, either inside the plan or by rolling it to a Roth IRA.
The catch is your employer has to allow it.
So before you dream about tax-free growth, you need to read your plan document or call HR and ask two specific questions: does the plan allow after-tax contributions, and does it allow in-service withdrawals or conversions?
If the answer is no to both, the strategy simply doesn't exist for you.
You can change jobs, sure, but that's an expensive way to chase a tax trick.
And a solo 401(k), which many self-employed people use, often does allow it, which is worth knowing if you're a freelancer or business owner.
The total 401(k) cap for 2025 sits around $70,000, and that includes your pre-tax or Roth deferrals plus any employer match.
If you're 50 or older, catch-up contributions push it higher.
The mega backdoor uses whatever room is left after the match.
After-tax contributions grow tax-deferred, but the earnings on them are taxable when converted to Roth.
If you let that money sit for years before converting, you could owe income tax on a sizable gain.
Convert quickly, ideally right after each paycheck, and the taxable portion stays small.
Some plans charge for each conversion, which can quietly eat the benefit.
There's also a five-year clock on Roth conversions and rules about accessing converted amounts early.
Pull money out too soon and penalties could follow.
The people pushing this hardest often have something to sell.
Advisors, custodians, and plan administrators all benefit from more assets under management.
That doesn't make the strategy bad, but it means the enthusiasm isn't purely altruistic.
For high earners who've maxed out every other tax-advantaged account, it can be a legitimate tool.
For everyone else, it's often a distraction from basic steps like an emergency fund, paying down high-interest debt, or just increasing a regular 401(k) deferral.
Our take: the mega backdoor Roth is a real option for a narrow slice of savers, not a hack that works for everyone.
If your plan allows it and you've done the math, fine.
Final Thoughts
If not, don't let anyone sell you a complicated workaround when a boring index fund and a higher deferral would do more.