What is a mega backdoor Roth?
Key takeaways
- The 2026 ceiling on everything that can go into your 401(k) is $72,000, and your own deferrals and your employer's money come out of that total first.1
- A mega backdoor Roth is a two-leg sequence, run inside a 401(k) rather than an IRA: after-tax contributions beyond the $24,500 deferral limit, then converted to Roth, either in-plan or rolled out to a Roth IRA.
- Most 401(k) plans don't allow a mega backdoor Roth, since it requires both after-tax contributions and a conversion route that the plan document has to permit explicitly.
In this article
- What is a mega backdoor Roth?
- What is the 2026 mega backdoor Roth limit?
- Does your 401(k) allow a mega backdoor Roth?
- Can a nondiscrimination test undo your mega backdoor Roth contributions?
- Should you convert your mega backdoor Roth in-plan or roll it out to a Roth IRA?
- How to do a mega backdoor Roth in 3 steps
- Frequently asked questions about the mega backdoor Roth
- Related posts
Key takeaways
- The 2026 ceiling on everything that can go into your 401(k) is $72,000, and your own deferrals and your employer's money come out of that total first.1
- A mega backdoor Roth is a two-leg sequence, run inside a 401(k) rather than an IRA: after-tax contributions beyond the $24,500 deferral limit, then converted to Roth, either in-plan or rolled out to a Roth IRA.
- Most 401(k) plans don't allow a mega backdoor Roth, since it requires both after-tax contributions and a conversion route that the plan document has to permit explicitly.
A mega backdoor Roth means making after-tax contributions to your 401(k) beyond the normal deferral limit, then converting them to Roth. In 2026 the total that can go into your 401(k) from every source is $72,000. Whatever's left after your own deferrals and your employer's money is your after-tax room.
What is a mega backdoor Roth?
A mega backdoor Roth is a two-leg sequence, run inside a 401(k) rather than an IRA: contribute after-tax dollars above the $24,500 deferral limit, then move them into Roth, either inside the plan or out to a Roth IRA. Neither leg has an income limit.
It's called "mega" for scale, not mechanics. The regular backdoor Roth moves $7,500 a year. This version can move tens of thousands.Our backdoor Roth guide covers the IRA version in full.
| Backdoor Roth IRA | Mega backdoor Roth | |
|---|---|---|
| Vehicle | Traditional IRA to Roth IRA | 401(k) after-tax to Roth |
| 2026 ceiling | $7,500 or $8,600 | Up to $72,000 minus everything else |
| Income limit | None | None |
| Main obstacle | Your other IRA balances | Whether your plan allows it |
The three kinds of 401(k) contribution
The strategy rests on a distinction that plan portals routinely blur:
- Pre-tax deferrals. No tax now, taxed on withdrawal. Counts against the deferral limit.
- Designated Roth deferrals. Taxed now, never taxed again. Also counts against the deferral limit.
- After-tax non-Roth contributions. Taxed now, and the earnings are taxed on withdrawal unless converted. This third bucket is the one the strategy actually uses, and it's a separate plan feature from the other two.
If your plan portal only offers "pre-tax" and "Roth," you probably don't have the third bucket. Plan websites frequently mislabel one as the other, which is worth double-checking before you assume the feature exists.
What is the 2026 mega backdoor Roth limit?
There's no separate "mega backdoor" limit written anywhere. There's one overall limit on everything going into your 401(k), and after-tax contributions fill whatever's left of it.
| Limit | 2026 |
|---|---|
| Total annual additions, §415(c) | $72,000 |
| Your own elective deferrals, §402(g) | $24,500 |
| Age 50+ catch-up, §414(v) | $8,000 |
| Ages 60–63 super catch-up | $11,250, unchanged from 2025 |
| Compensation limit, §401(a)(17) | $360,000 |
Start with the lesser of $72,000 or 100% of your compensation.4Subtract your own deferrals, your employer's match, any profit-sharing or non-elective contributions, and any forfeitures allocated to your account. What's left is your after-tax room, further capped by whatever percentage of pay your plan actually allows.
Two details most guides skip: the $72,000 figure is actually the lesser of that dollar amount or 100% of compensation, which binds first for anyone with modest pay, and forfeitures allocated to your account count toward the total too.
| Situation | Deferrals | Employer money | After-tax room |
|---|---|---|---|
| No employer contribution | $24,500 | $0 | $47,500 |
| 50% match on 6% of $200,000 | $24,500 | $6,000 | $41,500 |
| Generous profit sharing | $24,500 | $25,000 | $22,500 |
| Age 62, super catch-up | $24,500 + $11,250 | $6,000 | $41,500 |
Do catch-up contributions count toward the limit?
No. Catch-up contributions aren't annual additions and don't count against §415(c), under two separate regulations.3But a catch-up contribution has to be an elective deferral, pre-tax or designated Roth. An after-tax employee contribution can't be one.
Put those two facts together and catch-up neither reduces nor expands your after-tax room. It just raises the total you can put into the plan overall. At 50 or older, that ceiling is effectively $80,000. At 60 to 63, it's $83,250. Your after-tax room is the same either way.
If you read "your limit is $80,000" and plan $55,500 of after-tax contributions accordingly, your plan's recordkeeper will correct you. Separately, if your prior-year Social Security wages from that employer exceeded $150,000, SECURE 2.0 requires your 2026 catch-up to be Roth. That rule governs catch-up deferrals, not after-tax contributions, so it doesn't change this math.
Does your 401(k) allow a mega backdoor Roth?
Most plans don't. You need two separate features, not one.
- The plan has to permit voluntary after-tax employee contributions. This is the rarer of the two.
- The plan has to permit a conversion route: an in-plan Roth rollover, an in-service distribution of the after-tax subaccount, or both.
Look in your summary plan description under headings like "Employee After-Tax Contributions" and "In-Service Withdrawals." Both features need to be present. When you ask HR or your recordkeeper, three questions get you an unambiguous answer:
- Does the plan permit voluntary after-tax employee contributions, separate from Roth deferrals?
- Does it permit in-plan Roth rollovers, in-service distributions of the after-tax subaccount, or both?
- Is there an automatic conversion feature, and how often does it run?
Most plans cap after-tax contributions at a percentage of pay, often well below what $72,000 would otherwise allow. Ask for the actual percentage, not just whether the feature exists.
One route nobody covers: a solo 401(k) can be written to permit after-tax contributions and in-plan conversions, and with no employees, there's no nondiscrimination test to fail at all.
Can a nondiscrimination test undo your mega backdoor Roth contributions?
Yes, if you're a highly compensated employee and the plan fails its actual contribution percentage test. The ACP test compares the rate at which highly compensated employees make after-tax and matched contributions against the rate for everyone else. If the gap is too wide, the plan fails and has to fix it.
Safe harbor status doesn't exempt after-tax contributions. That's the point most articles miss entirely. A safe harbor plan offering employee after-tax contributions still has to pass the ACP test.3Safe harbor covers matching contributions only. If your prior-year compensation was above $160,000, you're the one exposed to this rule.
A failure means a corrective distribution of your after-tax contributions, plus whatever earnings they generated. That correction can land months into the following year, well after you've already converted the money. It happens more than you'd expect: plans with automatic conversion features often see low participation from non-highly-compensated employees, because the feature is opaque, and that's exactly what widens the gap that trips the test.
Should you convert your mega backdoor Roth in-plan or roll it out to a Roth IRA?
| In-plan Roth rollover | In-service rollout to a Roth IRA | |
|---|---|---|
| Where it lands | Designated Roth account in your 401(k) | Your Roth IRA |
| Five-year clock | Plan-specific, doesn't aggregate with your Roth IRA | Inherits your existing Roth IRA clock |
| Investments | The plan's menu | Anything |
| Fees | Often institutional share classes | Retail pricing |
| Access to basis | No contribution-basis ordering access | Ordering rules make basis available first |
| Creditor protection | ERISA anti-alienation | State law and bankruptcy code |
| Splitting off earnings | Not available | Available under Notice 2014-54 |
The strongest argument for the rollout route is the clock. If you've already held a Roth IRA for years, money rolled into it inherits that already-satisfied clock. Money converted in-plan starts a separate, plan-specific one instead. Some plans only offer one of the two routes, which makes the comparison moot in practice.
What happens to the earnings before you convert
After-tax money that sits earns something while it waits, and that growth is pre-tax. Convert it and those earnings become taxable income for the year. How much drift you see depends entirely on your plan's conversion cadence: some convert daily and automatically, some batch quarterly, and some require you to call and ask.
There's an escape hatch almost nobody names: IRS Notice 2014-54.2Because disbursements scheduled at the same time count as a single distribution, you can direct your after-tax basis to a Roth IRA and the pre-tax earnings to a traditional IRA, tax-free, as long as you tell the plan administrator before the rollovers happen. This only works on the rollout route.
The IRA pro-rata rule doesn't reach your 401(k) after-tax subaccount, because the aggregation rule only applies to individual retirement plans, and a defined contribution plan's employee contributions can be treated as a separate contract under a different code section.4That treatment is permissive rather than automatic, and pro-rata still applies within the after-tax subaccount itself, between your basis and its own earnings.
How to do a mega backdoor Roth in 3 steps
- Max your elective deferrals, then work out your remaining §415(c) room using your actual employer contributions, not an estimate.
- Elect after-tax contributions through your plan, up to the lower of that room and your plan's percentage-of-pay cap.
- Convert as soon as the plan permits. Automatic conversion, where it's offered, is the cleanest option, since it keeps the taxable earnings sliver close to zero.
Expect a Form 1099-R for the conversion, with the gross amount in Box 1, the taxable amount in Box 2a, your after-tax basis in Box 5, and distribution Code G in Box 7a. The 2026 revision renumbered the old Box 7 to Box 7a; Code G itself didn't change.5
Frequently asked questions about the mega backdoor Roth
Does a mega backdoor Roth affect my regular Roth IRA contribution limit?
No, a mega backdoor Roth doesn't affect your regular Roth IRA contribution limit, because the two limits are entirely separate. Your 401(k) sits under the annual additions limit, and your IRA sits under its own, much smaller limit. Doing one doesn't reduce the other, so it's possible to fund both a mega backdoor Roth and a regular backdoor Roth in the same year.
Can I do this if I earn too much for a Roth IRA?
Yes, you can do a mega backdoor Roth even if you earn too much for a Roth IRA, because income limits don't apply here at all. The Roth IRA MAGI phase-out only governs direct contributions to an IRA. Neither an after-tax 401(k) contribution nor a conversion has an income limit, which is the entire reason high earners use this route in the first place.
Can I withdraw the converted money early?
Whether you can withdraw the converted money early depends on which route you used. Money rolled to a Roth IRA is generally accessible under the ordering rules, which make basis available first. Money converted in-plan to a designated Roth 401(k) doesn't have that same basis-first access, because it's still governed by the plan's own distribution rules.
Does converting after-tax 401(k) money start a new five-year clock?
Only partly: converting after-tax 401(k) money starts a new five-year clock just for the taxable sliver of that conversion. The recapture clock counts just the portion of a conversion includible in gross income, and your after-tax basis was never includible in the first place. If you roll the money into a Roth IRA you've already held for years, it inherits that account's already-satisfied qualified-distribution clock.
What are my options if my plan doesn’t allow this?
If your plan doesn't allow a mega backdoor Roth, since it's missing one of the two required features, the realistic alternatives are a regular backdoor Roth, a health savings account if you have a qualifying plan, or a plain taxable brokerage account. It's also worth asking your plan sponsor directly whether they'd consider adding the feature.
Nicolas Straut
Personal finance writer, former Forbes contributor and This Week in Fintech writer
Whether this strategy is available to you depends entirely on your employer’s plan document, contributions can be returned if the plan fails nondiscrimination testing, and 2026 figures come from IRS Notice 2025-67. Tweed provides educational estimates, not financial advice. Confirm your specific situation with a qualified tax professional.
Sources
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