Buried in the fine print of many workplace retirement plans is a feature that lets you shelter far more money from taxes than the standard $23,000 annual limit.
It has a clunky nickname: the mega backdoor Roth.
And most people who could use it have never heard of it.
A regular 401(k) lets you contribute up to $23,000 in 2024, or $30,500 if you are 50 or older.
But the total amount that can flow into your plan, including employer matches, caps out much higher—$69,000 this year, or $76,500 with catch-up contributions.
The mega backdoor Roth is a maneuver that lets you fill the gap between those two numbers with your own after-tax dollars, then convert that money into a Roth account.
The result: years of tax-free growth on tens of thousands of dollars a year, far beyond what a normal Roth IRA allows.
You need two specific features in your 401(k): the ability to make after-tax contributions (not the same as Roth contributions), and either in-plan conversions or the option to roll that money into a Roth IRA.
If your plan lacks these, the door is locked.
The catch is that this is not a loophole for everyone.
It mostly benefits high earners who already max out their regular 401(k), have spare cash, and work for an employer generous enough to include these features.
According to retirement researchers, only a minority of plans actually offer them.
If you think your plan might, the first move is boring but essential: pull out your summary plan description or log into your provider's site and search for "after-tax contributions." If you find it, call your plan administrator and ask exactly how the conversion works, because the tax bill depends on timing.
If you convert after-tax money that has already grown, you owe income tax on the gains.
If you convert immediately, the taxable amount is usually near zero.
Many plans now allow automatic same-day conversions for exactly this reason.
Contribution caps are indexed to inflation and can shift each year.
Your plan may restrict how often you can convert.
And if you leave your job, you generally roll the Roth portion into a Roth IRA and the pre-tax portion into a traditional one.
But for a certain slice of workers, this is one of the few remaining ways to move serious money into tax-free territory without earning a business or buying real estate.
Before you assume your 401(k) is just a match and a dream, dig into the paperwork.
Final Thoughts
The most valuable feature in your plan may be the one nobody bothered to mention.