If you’re self-employed and trying to save for retirement, you’ve likely come across two common options: the SEP IRA and the Solo 401(k).
At a glance, they look similar. Both allow for tax-deferred savings. Both are relatively easy to set up. Both are designed for business owners without full-time employees. But under the surface, they function very differently, and choosing the right one can meaningfully impact how much you’re able to save.
The Key Difference: How Contributions Work
A SEP IRA is simple:
You contribute as the employer only, up to 25% of compensation (with an annual cap).
A Solo 401(k) gives you two ways to contribute:
• As the employee (salary deferral)
• As the employer (profit-sharing)
This dual structure is what makes the Solo 401(k) so powerful, especially at lower income levels.
Why Solo 401(k)s Often Win
If your income is under ~$300,000, the Solo 401(k) typically allows for higher total contributions.
Why? Because you can make employee contributions (up to the annual limit) on top of employer contributions.
With a SEP IRA, you’re limited to that single 25% calculation, meaning it often takes a much higher income to reach the same contribution level.
When a SEP IRA Might Make Sense
Despite its limitations, the SEP IRA still has a role:
- You want maximum simplicity
• Your income is already high enough to hit contribution limits
• You’re not interested in ongoing plan administration
• You may eventually add employees (SEP rules are more flexible here)
It’s the “set it and forget it” option.
Other Considerations That Matter
A few nuances often get overlooked:
- Roth option: Solo 401(k)s can allow Roth contributions; SEPs cannot
• Loans: Solo 401(k)s may allow loans; SEPs do not
• Backdoor Roth strategy: SEP IRAs can complicate this due to pro-rata rules
These details can quietly shape your broader financial strategy.
The Bottom Line
For many self-employed individuals, especially those early in their earning curve, the Solo 401(k) offers more flexibility and higher contribution potential.
But the “best” choice isn’t universal. It depends on your income, business structure, and how hands-on you want to be.