Calculate your mega backdoor Roth contribution space and see how much extra tax-free wealth you can build.
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| 415(c) Limit | $69,000 |
|---|---|
| Employee Deferrals | $23,000 |
| Employer Match | $8,000 |
| Mega Backdoor Space | $38,000 |
| Total Mega Contributions (25yr) | $950,000 |
| Additional Wealth from Mega Backdoor | $2,403,464 |
| Est. Tax Savings (22% bracket) | $528,762 |
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The mega backdoor Roth is a strategy that lets high earners contribute significantly more to Roth accounts than normal limits allow. Here's how the 401(k) contribution limits stack up in 2024:
• Employee elective deferrals: $23,000 ($30,500 if 50+)
• Employer match: varies by plan
• After-tax contributions: up to the overall 415(c) limit
• Total 415(c) limit: $69,000 ($76,500 if 50+)
The"mega backdoor" is the gap between your employee deferrals + employer match and the $69,000 total limit. That gap can be filled with after-tax contributions, then converted to Roth.
1. Max out your pre-tax or Roth 401(k) contributions ($23,000)
2. Receive your employer match
3. Make after-tax contributions up to the remaining room under $69,000
4. Convert those after-tax dollars to Roth (either in-plan conversion or rollover to Roth IRA)
5. Future growth is now tax-free in Roth
The key: you only pay tax on any gains between contribution and conversion. If you convert immediately (same day or next business day), gains are negligible and the conversion is essentially tax-free.
The mega backdoor Roth is ideal for:
• High-income earners who already max out 401(k) and IRA contributions
• Anyone who wants more tax-free growth space beyond $23,000/year
• People who expect to be in a higher tax bracket in retirement
• Those with plans that allow after-tax contributions AND in-plan Roth conversions
After-tax contributions are made with post-tax dollars (no deduction). When converted to Roth:
• The contribution amount converts tax-free (you already paid tax)
• Any gains between contribution and conversion are taxed as ordinary income
• Once in Roth, all future growth and withdrawals are tax-free (after age 59½ and 5-year rule)
This is why immediate conversion is critical — minimize the taxable gains window.
• Your plan must allow after-tax contributions (many don't)
• Your plan must allow in-plan Roth conversions or in-service distributions
• Pro-rata rule applies if rolling to a Roth IRA with existing traditional IRA balances
• Congress has proposed eliminating this strategy (Build Back Better Act) — it may not last forever
• Reduces your current cash flow significantly
The total 415(c) limit is $69,000 ($76,500 if 50+). Your mega backdoor Roth space is $69,000 minus your employee deferrals minus employer match.
Yes. Both after-tax contributions AND in-plan Roth conversions (or in-service distributions) must be allowed. Check with your plan administrator.
No. The regular backdoor Roth involves a nondeductible Traditional IRA → Roth IRA conversion (limit ~$7,000/year). The mega backdoor uses after-tax 401(k) contributions (up to ~$46,000 extra).
Gains on after-tax contributions will be taxed as ordinary income when converted. Convert as soon as possible — ideally the same day — to minimize taxable gains.
Yes, if you have a Solo 401(k) that allows after-tax contributions and in-plan Roth conversions. Many Solo 401(k) providers support this.
First, make after-tax contributions to your 401k above the standard $23,000 limit. Then convert or roll over those after-tax contributions to a Roth IRA or Roth 401k. This lets you contribute up to $69,000 total to retirement accounts in 2024.
Yes, your 401k plan must allow after-tax contributions and permit either in-service Roth conversions or in-service distributions. Not all employers offer this. Check with your HR department or plan administrator to verify your plan supports these features.
After-tax contributions convert to Roth tax-free since you already paid tax on them. However, any investment gains on those contributions are taxable upon conversion. Convert frequently to minimize taxable gains that accumulate between conversions.
A regular backdoor Roth involves contributing $7,000 to a non-deductible traditional IRA then converting to Roth. A mega backdoor Roth uses after-tax 401k contributions up to $46,000 additional, converting much larger amounts to Roth accounts.
High earners who have already maxed their standard 401k and IRA contributions benefit most. It is especially valuable for those in high tax brackets now who expect similar or higher taxes in retirement, and those seeking to maximize Roth assets.
Mega Backdoor Space = 415(c) Limit − Employee Deferrals − Employer Match
2024 415(c) limit: $69,000 ($76,500 if age 50+). Employee deferral limit: $23,000 ($30,500 if 50+).
FV = Contributions × [(1+r)^n − 1] / r for projected growth of annual contributions.
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Calculations are for educational purposes only. Consult a qualified financial advisor for personalized advice.