Solo 401k Contribution Limits 2025
Solo 401(k) contribution limits and tax benefits for 2025
| Contribution Type | 2025 Limit | Tax Benefit | Reduces SE Tax? |
|---|---|---|---|
| Employee contribution (traditional) | $23,500 | Pre-tax — reduces income tax | No |
| Employee contribution (Roth) | $23,500 | After-tax — no current deduction | No |
| Employee catch-up (age 50+) | +$7,500 | Pre-tax — reduces income tax | No |
| Employer contribution | 25% of net SE income (up to $46,500) | Pre-tax — reduces income AND SE tax | Yes |
| Total annual addition limit | $70,000 (under 50) / $77,500 (50+) | Large shelter | Yes (employer portion) |
At $100,000 net SE income: Solo 401k allows $23,500 (employee) + $18,500 (employer) = $42,000. SEP-IRA allows only $18,500 (employer). Solo 401k saves approximately $5,940 more in SE + income taxes due to the additional $23,500 employee contribution space.
How the Employer Contribution Reduces SE Tax
The Solo 401k employer contribution is deducted as a business expense on Schedule C, reducing net SE income. On $100,000 net income with $18,500 employer contribution: net SE income drops to $81,500. SE tax on $81,500: $11,520. SE tax without the contribution: $14,130. Tax savings from employer contribution alone: $2,610 in SE tax + approximately $4,070 in income tax at 22% = $6,680 in total tax savings from the $18,500 employer contribution.
Contribution Formula for 2025
Employer contribution = 25% × (net SE income − SE tax deduction). Simplified: 20% × net SE income (rough approximation). Exact calculation requires the exact SE tax deduction for your income level. The calculator handles this automatically for precision.
Calculate Your Solo 401k Tax Savings
Enter your net SE income to see your maximum Solo 401k contribution and the exact SE and income tax savings it generates.