SEP IRA vs Solo 401(k): Self-Employed Retirement Plans

If you are self-employed, choosing the right retirement plan can save you tens of thousands in taxes over your career. The SEP IRA and Solo 401(k) are the two dominant options, and the right choice depends on your income level, contribution goals, and desire for flexibility.

SEP IRA: Simplicity and Speed

The Simplified Employee Pension IRA is exactly what its name suggests: simple. You can open one in minutes at any major brokerage, contributions are tax-deductible, and the paperwork is minimal. There are no annual filing requirements with the IRS until account balances become very large.

For 2024, you can contribute up to 25% of your net self-employment income, with a maximum of $69,000. Net self-employment income is your business profit minus half of your self-employment tax, so the effective contribution rate is closer to 20% of gross Schedule C profit for sole proprietors.

The SEP IRA shines for high earners who want a dead-simple plan. If you earn $300,000 or more in net self-employment income, you can hit the $69,000 maximum without complex calculations. Contributions are entirely employer contributions (even though you are both the employer and employee), which simplifies the contribution calculation.

Solo 401(k): Power and Flexibility

The Solo 401(k), also called an Individual 401(k) or one-participant 401(k), offers more features but requires slightly more administrative effort. It is available to self-employed individuals with no employees other than a spouse.

The key advantage is the dual contribution structure. You can make both employee deferrals (up to $23,000 in 2024, plus $7,500 catch-up if over 50) and employer contributions (up to 25% of net self-employment income). The combined total cannot exceed $69,000 ($76,500 with catch-up).

The Income Crossover Point

For self-employed individuals, the crucial question is: at what income level does each plan allow the maximum contribution? This is where the Solo 401(k) has a decisive advantage for most self-employed workers.

The gap narrows as income increases. At approximately $270,000 in net self-employment income, both plans converge at the $69,000 maximum. Above that level, the contribution capacity is identical and the decision comes down to features and simplicity.

For income below about $200,000, the Solo 401(k) almost always allows significantly higher contributions because the employee deferral portion acts as a flat contribution that is not limited by income percentage. A freelancer earning $50,000 can put away $23,000 in employee deferrals plus roughly $9,300 in employer contributions for a total of $32,300 in a Solo 401(k), versus only about $10,000 in a SEP IRA.

The Roth Factor

If tax-free retirement income is a priority, the Solo 401(k) wins by default. SEP IRAs are entirely pre-tax, with no Roth option available. The Solo 401(k) allows you to designate your employee deferrals as Roth contributions, meaning you pay tax on those dollars now but never pay tax on the growth or withdrawals.

For self-employed workers who expect their tax rate to be higher in retirement (or who want the flexibility of tax-free withdrawals), the Roth option is a significant differentiator. You can even split your employee deferrals between pre-tax and Roth within the same plan.

Additionally, the Solo 401(k) enables the mega backdoor Roth strategy. If your plan allows after-tax contributions and in-plan Roth conversions, you can funnel the full $69,000 (or $76,500) into Roth treatment. This is not possible with a SEP IRA under any circumstances.

When to Choose the SEP IRA

Despite the Solo 401(k)'s advantages, the SEP IRA is the better choice in specific situations. If you have very high self-employment income (above $270,000) and don't need Roth or loan features, the SEP IRA's simplicity wins. You also benefit from the extended contribution deadline if you need more time to determine your optimal contribution amount.

The SEP IRA is also simpler if you plan to hire employees in the future. While a SEP requires employer contributions for all eligible employees at the same percentage as the owner, the plan itself scales more easily. A Solo 401(k) must be terminated or converted to a standard 401(k) once you hire non-spouse employees, which adds complexity.

How Talk Through Wealth Helps

Choosing between a SEP IRA and Solo 401(k) depends on your current income, growth trajectory, tax strategy, and retirement goals. Our projection engine models both plans side by side with your specific income data, showing you the year-by-year contribution differences, tax impact, and long-term wealth accumulation. See how each plan performs across different income scenarios and which one gets you to your retirement goal faster.