· Listen
This lesson has not yet been reviewed by a CFP or CPA. The mechanics and figures here are sourced to IRS guidance on 401(k) and profit-sharing contribution limits and the 2026 limit release. Whether your plan allows after-tax contributions and in-plan Roth conversions is specific to your employer's plan document. Consult a licensed advisor before acting on a specific situation.
The mega backdoor Roth is a strategy that lets high earners contribute substantially more to a Roth account than the standard limits, sometimes $40,000+ per year on top of normal contributions. It only works if your employer's 401(k) plan supports two specific features.
The two requirements
- Your 401(k) plan must allow after-tax contributions (different from Roth contributions)
- Your plan must allow either in-service distributions to a Roth IRA, or in-plan Roth conversions
Big tech companies, large law firms, and many financial services employers commonly offer this. Smaller employers usually don't.
How the math works
The total 401(k) contribution limit (employee + employer + after-tax) is $72,000 in 2026 (the IRS § 415(c) overall limit). If you max your normal employee contribution at $24,500 and your employer adds $10,000 in matching, that leaves $37,500 of unused space you can fill with after-tax contributions, then convert to Roth.
Why it's so powerful
All of that money grows tax-free forever and comes out tax-free in retirement. For high earners maxing every other tax-advantaged account, this is one of the largest remaining buckets of tax-free growth available.
Ask your HR or 401(k) plan administrator: 'Does our plan allow after-tax contributions and in-plan Roth conversions?' If both answers are yes, you have access to the mega backdoor. Educational only. Confirm specifics with your plan.
What this lesson is NOT
This is not tax advice, and it only works if your specific 401(k) plan allows after-tax contributions and in-plan Roth conversions. Many plans do not. The limits and rules can change, so confirm the details with your plan administrator and, for large amounts, a tax professional.
Quick check on this lesson
Answer each question and we’ll show you why the right answer is right, and why the others aren’t.
- 1.
What does the mega backdoor Roth let high earners do, per the lesson?
- 2.
Per the lesson, what two features must your 401(k) plan support for the mega backdoor Roth to work?
- 3.
Per the lesson's example with the 2026 numbers, $24,500 normal employee contribution and $10,000 employer match, how much after-tax mega backdoor space remains, given the $72,000 total 401(k) limit?
- 4.
Per the lesson, why is the mega backdoor Roth so powerful for high earners?
- 5.
Per the tax callout, what specific question should you ask your HR or 401(k) plan administrator?
0 of 5 answered