By Kevin Luu, Co-Founder and Chief Learning Officer. Reviewed on 2026-09-30.
The super backdoor Roth (usually called the mega backdoor Roth) means making after-tax contributions to your 401(k) above the normal $24,500 deferral limit, then converting that money to Roth so future growth is tax-free. For 2026, total contributions to one person’s 401(k) can reach $72,000 before catch-ups, so a high-income employee whose plan allows it can often move $30,000 to $45,000 a year into Roth, with no income limit. It only works if your employer’s plan allows both after-tax contributions and an in-plan Roth conversion or in-service withdrawal.
For a household earning $750,000 to $3 million, this is one of the few ways left to build a large Roth balance. You are far above the 2026 Roth IRA income phase-out ($242,000 to $252,000 for married couples filing jointly), and a regular backdoor Roth IRA moves only $7,500 per person. The mega version can move four to six times that, through payroll, every year.
How the super backdoor Roth works in a 401(k)
A 401(k) can hold three kinds of employee money: pre-tax deferrals, Roth deferrals, and after-tax (non-Roth) contributions. Most people only use the first two, which share the $24,500 limit for 2026 under IRC §402(g). The after-tax bucket sits on top of that, inside the larger overall limit for all additions to the account.
That overall limit (IRC §415(c)) is $72,000 for 2026 and counts your deferrals, your employer’s match or profit sharing, and your after-tax contributions together. Catch-up contributions for people 50 and older are outside it (IRS Notice 2025-67 for the limit; IRC §414(v)(3)(A) for the catch-up rule). So your room is:
After-tax room = $72,000 minus your deferrals minus your employer’s contributions.
On its own, after-tax money is not very useful: the contribution is not deductible and the earnings are taxed as ordinary income when withdrawn. The value comes from the second step. You convert the after-tax dollars to Roth, either inside the plan (an in-plan Roth conversion) or by rolling them out to a Roth IRA through an in-service withdrawal. Once the money is Roth, qualified withdrawals of both contributions and growth are income-tax-free.
The conversion itself is mostly tax-free because you already paid tax on the contribution. Only the earnings between contribution and conversion are taxable. IRS Notice 2014-54 lets you send the after-tax basis to a Roth IRA and any pre-tax earnings to a traditional IRA in the same distribution. Many large employers now offer automatic daily conversion, which keeps those taxable earnings close to zero.
Three things that go by “super Roth”
Search results mix up three different strategies. Only one of them is the subject of this article.
| Backdoor Roth IRA | Super (mega) backdoor Roth | “Super Roth” life insurance | |
|---|---|---|---|
| What it is | Nondeductible traditional IRA contribution, then conversion to Roth IRA | After-tax 401(k) contributions, then conversion to Roth | A marketing name for cash-value life insurance, often indexed universal life |
| 2026 amount per person | $7,500 ($8,600 at 50+) | Up to $72,000 minus deferrals and employer money | No IRS contribution limit; set by the policy design |
| Income limit | None for the conversion | None | None |
| Main trap | Pro-rata rule if you hold other pre-tax IRA money (Form 8606) | Plan must allow it; testing limits for highly compensated employees | Insurance charges, surrender periods, and loans that can create tax if the policy lapses |
| Is it a Roth account? | Yes | Yes | No. Tax treatment comes from life insurance rules (IRC §7702) |
If you were shown a “super Roth” in an insurance presentation, it is a life insurance policy, not a retirement account, and should be judged on whether you need permanent coverage. We cover that comparison in What is a 7702?. The backdoor Roth IRA and its pro-rata rule are covered in our backdoor Roth IRA guide.
Worked example: a $950,000 household in the Bay Area
Assumptions (illustrative): Maya, 38, is a scientist at a South San Francisco biotech earning a $420,000 salary plus RSUs. Her husband Daniel, 40, is an engineer at a Cupertino tech company. Household W-2 income is about $950,000, married filing jointly, two children ages 4 and 7. Both plans allow after-tax contributions with automatic Roth conversion.
- Deferrals. Maya contributes the full $24,500 for 2026.
- Employer match. Her plan (hypothetically) matches 50% of the first 6% of pay. Pay counted for plan purposes is capped at $360,000 for 2026 under IRC §401(a)(17), so the match is $360,000 x 6% x 50% = $10,800.
- After-tax room. $72,000 minus $24,500 minus $10,800 = $36,700.
- Daniel. If his plan has a similar match, he has roughly the same room. Together they could move about $73,400 a year into Roth, on top of their regular deferrals.
What that is worth: if Maya contributes $36,700 a year for ten years and it earns an assumed 6% a year, she ends with about $483,700, of which about $116,700 is growth. In a Roth, that growth comes out tax-free in retirement if the withdrawal is qualified.
Had she invested the same money in a taxable brokerage account in California and sold at the end, the growth would face 20% federal long-term capital gains tax (their taxable income is above the $613,700 threshold for 2026), 3.8% net investment income tax, and California tax at ordinary rates, since California taxes capital gains as ordinary income. Most of this gain would land in California’s 11.3% joint bracket ($891,542 to $1,485,906 of taxable income for 2025, the latest published schedule). That is about 35.1% combined, or roughly $41,000 on the $116,700 of growth, before counting annual tax on dividends along the way. A household with California taxable income above $1 million would pay up to 13.3% to the state, or 37.1% combined. Over a 25-year horizon the gap grows much larger.
California versus Washington
California. The Roth shelter is worth more here than almost anywhere. The top rate is 13.3% for 2025 (12.3% plus the 1% Behavioral Health Services Tax on income over $1 million), and there is no lower rate for capital gains. Every dollar of growth kept out of a taxable account avoids that.
Washington. There is no tax on wages in 2026. The state’s capital gains tax (7% on long-term gains, 9.9% on gains above $1 million) exempts retirement accounts, and it only applies above an annual standard deduction ($278,000 for 2025, the latest published figure) (WA DOR). So for many Washington families the main benefit is federal. Note that Washington has enacted a 9.9% income tax on AGI above $1 million starting in 2028 (WA DOR). How that tax will treat retirement distributions is still pending guidance, which is another reason to value money that is already Roth.
How to set it up: five steps
- Read your plan’s summary plan description. Look for “after-tax contributions” (not the same as Roth deferrals) and either “in-plan Roth conversion” or “in-service withdrawals of after-tax money.” Many large tech and biotech employers offer both. Some plans cap after-tax contributions at a percentage of pay.
- Max your regular deferrals first. The after-tax bucket is only useful once the $24,500 is covered. Decide separately whether those deferrals should be pre-tax or Roth.
- Calculate your room using the formula above, including your full-year employer match and any true-up.
- Turn on automatic conversion if offered. If it is not, convert on a regular schedule so taxable earnings stay small.
- Keep the paperwork. The plan reports the year’s conversions or rollovers on Form 1099-R. Your tax preparer needs it to show that only the earnings were taxable.
Common mistakes high earners make
- Front-loading and losing the match. If you hit the $24,500 deferral limit by May, some plans stop matching for the rest of the year unless they have a true-up. Check before you set a high percentage.
- Ignoring nondiscrimination testing. After-tax contributions are part of the ACP test. In 2026, employees who earned more than the $160,000 HCE threshold in the prior year can have some after-tax contributions refunded if the plan fails the test, which compares their matching and after-tax contribution rates with those of other employees (IRS fix-it guide). Plans with broad participation are less likely to fail; smaller practices and startups are more exposed.
- Leaving after-tax money unconverted for years. The earnings build up as pre-tax money and are taxed at conversion.
- Assuming it affects your backdoor Roth IRA. The pro-rata rule for the backdoor Roth IRA looks at your IRA balances, not your 401(k). The two strategies can run side by side. One catch: if you roll pre-tax earnings out to a traditional IRA (the Notice 2014-54 split above), that IRA balance does count toward the pro-rata calculation.
- Counting on it for near-term cash. Roth money is best left for the long run. Withdrawal rules for converted money are technical; see our mega backdoor Roth withdrawal rules before planning on it for a house or tuition.
The decision: Roth, brokerage, or something else
The real question is not whether the strategy works. It is whether this cash should be locked into retirement accounts at all. A family saving for a Bay Area or Seattle home in the next three years, or still building a cash reserve, may be better served by keeping some flexibility. A family with concentrated RSUs may want to direct new savings toward diversification. We compare those trade-offs in Mega Backdoor Roth vs Brokerage.
For long-term money, Roth has two extra advantages for parents. Roth 401(k) accounts and Roth IRAs have no required minimum distributions during the owner’s lifetime (IRS RMD FAQs), and qualified Roth withdrawals by heirs are generally income-tax-free. That makes Roth one of the cleaner assets to leave to children, which brings estate planning into the same conversation.
What to write down for your kids
Your children will not remember your 401(k) elections. They might remember why you chose to give up spending money today so their future selves would have tax-free money. A one-page note in your FamilyKnowledge® Library explaining what the mega backdoor Roth is, why you used it, and what you gave up for it is a lesson they can read at 16. As Kevin Luu puts it: “Your kids don’t need to inherit your portfolio. They need to inherit your decision-making process.”
Frequently asked questions
Is there an income limit for the mega backdoor Roth?
No. Unlike direct Roth IRA contributions, which phase out at $242,000 to $252,000 of MAGI for married couples filing jointly in 2026, after-tax 401(k) contributions and Roth conversions have no income limit. The practical limits are your plan’s rules and, for highly compensated employees, whether the plan passes its annual nondiscrimination test.
Can both spouses do it?
Yes, if both employer plans allow after-tax contributions and conversions. The $72,000 limit for 2026 applies to each person, so with separate employers a dual-income couple can often move $60,000 to $90,000 a year into Roth combined. Each spouse’s room depends on their own deferrals and employer contributions.
Is “super Roth” life insurance the same thing?
No. “Super Roth” is a sales name some insurers use for cash-value life insurance. It is not a Roth account and is not governed by Roth rules. It can make sense for a family that needs permanent coverage, but its costs and loan features are different, so evaluate it as insurance, not as a substitute for the mega backdoor Roth.
Next step
Pull your plan’s summary plan description this week and search for “after-tax.” If both you and your spouse have the feature, the math above shows what it could be worth. If you would like a second set of eyes on how it fits with your RSUs, employee benefits and tax planning, that is part of the Tax & Wealth Assessment at the Age Five Family Office™.
This is general education, not individual tax advice. The right move depends on your family’s full picture and your plan’s specific rules.
Kevin has advised high-income W-2 tech and biotech families since 2015, and leads the education-first Age Five Family Office from Brea, California.
Connect on LinkedIn → · About KevinThis is part of how we approach Tax Management for high-income W-2 families at Bright Advisers.
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