Mega Backdoor Roth: $46.5k After-Tax Contribution Strategy
Quick Answer
After-tax 401(k) contributions: Up to $46.5k additional (2026 total limit $69k minus $23.5k employee deferral). Immediately convert to Roth (no pro-rata rule applies). Combined with regular backdoor Roth IRA ($7k) = $53.5k/year Roth for high earners.
Two Types
In-service conversions: After-tax contributions immediately converted to Roth (most common). Minimize taxes.
In-service distributions: After-tax distributed during employment (less favorable). Requires plan to allow.
Step-by-Step
- Check plan (ask administrator)
- Contribute up to $46.5k after-tax
- Request conversion to Roth
- Funds appear in Roth 401(k) or Roth IRA
- File Form 8606 (minimal tax if immediate)
2026 Limits
| Source | Limit |
|---|---|
| Employee deferral | $23,500 |
| After-tax contributions | $46,500 |
| Total 401(k) | $69,000 |
No Pro-Rata Rule
After-tax contributions NOT subject to pro-rata rule (only gain is taxable). Huge advantage vs. Roth conversions.
Combining Mega + Regular Backdoor
- Mega backdoor Roth 401(k): $46.5k
- Regular backdoor Roth IRA: $7k
- Total: $53.5k/year Roth
Married couple: $107k/year combined.