Most people know the drill when it comes to retirement accounts: you can put money into a 401(k), maybe a Roth IRA if you qualify, and that's about it.
But there's a lesser-known maneuver with a goofy name that lets certain savers sock away far more than the standard limits — and it's completely legal.
It's called the "mega backdoor Roth," and despite the name, it has nothing to do with sneaking around.
It's a two-step process that takes advantage of a feature some workplace plans already offer.
For high earners who've maxed out every other option, it can mean tens of thousands of extra dollars growing tax-free.
In 2024, you can contribute up to $23,000 to a 401(k) from your paycheck, or $30,500 if you're 50 or older.
But that's not the only limit that matters.
There's a second, bigger ceiling — $69,000 total for 2024 — that includes your contributions plus whatever your employer kicks in.
If your company matches generously and you still have room under that higher cap, some plans let you add after-tax dollars to fill the gap.
Those after-tax dollars don't grow tax-free on their own, which is why step two matters.
You then convert that after-tax money into a Roth account, either inside your 401(k) if your plan allows it or by rolling it into a Roth IRA.
Once it's in Roth territory, the growth and future withdrawals can come out tax-free in retirement, assuming you follow the rules.
The catch is that this only works if your employer's plan offers after-tax contributions and either in-plan conversions or the ability to roll money out.
You'll need to check your plan documents or call your HR benefits line and ask a very specific question: does our 401(k) allow after-tax contributions and in-service Roth conversions?
If the answer is yes, the payoff can be significant.
Someone with enough spare cash could potentially move an extra $20,000 or more into Roth territory each year — money that would otherwise sit in a taxable account.
Over a decade, that difference compounds in a big way.
This strategy is aimed at people who've already maxed out their regular 401(k) and probably a Roth IRA too.
Second, the IRS has rules about how conversions are taxed, and if you have money sitting in a traditional IRA, the math can get messy.
A tax professional is worth the fee here.
Third, and this is the part people miss: many plans limit how often you can do the conversion, or they charge fees.
If the market moves a lot between your after-tax contribution and the conversion, you could owe taxes on the gains.
The mega backdoor Roth isn't for everyone, and it's not a magic bullet.
But for a certain slice of American workers — steady paycheck, generous employer match, and a plan that allows it — it's one of the few remaining ways to shelter a serious amount of money from taxes.
Our take: this is a niche tool, not a household staple, and it's frustrating that it depends entirely on whether your employer's plan happens to offer it.
If you're lucky enough to have access, it's worth a conversation with a tax pro before the year ends.
Final Thoughts
If you don't, don't lose sleep — maxing out a regular 401(k) and a Roth IRA still puts you ahead of most people.