💼 SEP IRA vs Solo 401(k) — Which Retirement Plan Truly Works Best for Self-Employed Individuals? (2026 Guide)
If you’re self-employed, freelance full-time, or run a one-person LLC, you’ve probably wondered :“Should I open a SEP IRA or a Solo 401(k)? Which one actually gives me the bigger tax break?”
Both plans are powerful, but their rules, contribution mechanics, and advantages are very different. Choosing the wrong one could limit your tax savings for the entire year.
1️⃣ How a SEP IRA Works
• Only employer contributions are allowed
• If you have employees, you must contribute the same percentage for everyone
• Simple to set up and easy to maintain
A SEP IRA is essentially an employer-funded plan.
If you’re self-employed, you act as your own employer — meaning the contribution is made from your business.
Contributions are based on a formula tied to your net earnings (if you’re a sole proprietor) or your W-2 wages (if you’re an S Corporation owner).
The structure is simple, but the lack of Roth and employee deferral options makes it less flexible for many business owners.
• Sole proprietors → % of net earnings
• S Corp owners → % of W-2 payroll
2️⃣ How a Solo 401(k) Works
Unlike a SEP IRA, a Solo 401(k) lets you wear both hats — employee and employer.
This dual structure gives you more flexibility and often a higher contribution ceiling at lower income levels.
• Employee deferral + employer contribution
• Roth deferral may be available depending on the plan
• Catch-up contributions allowed at age 50+
• Loan options available in many plans
• No W-2 employees allowed (other than your spouse)
Even though the PDF you provided focuses on traditional IRAs, the general retirement plan rules still apply: employee contributions, employer contributions, and an overall IRS limit.
- Employee deferral — up to the annual IRS limit
- Employer contribution — based on business income
- Combined limits — subject to overall 2026 IRS maximums
Because you can contribute in two different ways, the Solo 401(k) often reaches the maximum contribution much faster than a SEP.
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3️⃣ Key Differences Between the Two
① Contribution Structure
• SEP: employer contribution only
• Solo 401(k): employee deferral + employer contribution
② Roth Availability
• SEP: not available
• Solo 401(k): Roth deferral may be available
③ Employee Rules
• SEP: employees must receive equal-percentage contributions
• Solo 401(k): employees not allowed (except spouse)
④ Efficiency at Lower Income Levels
• SEP: contributions grow only as income grows
• Solo 401(k): high limits possible even at modest income due to employee deferral
4️⃣ Real-Life Example — Which One Wins?
▪ 2025 net earnings: $90,000
▪ No employees
▪ Prefers Roth flexibility
SEP IRA Scenario
• Only employer contributions allowed
• No Roth option
• Contribution grows only as income increases
Solo 401(k) Scenario
• Employee deferral + employer match
• Roth deferral possible
• Higher contribution limit achievable at this income range
✔ Result: With these factors, a Solo 401(k) provides more flexibility and more room to save.
But if you have employees or extremely high business income,
a SEP IRA may align better with your structure.
5️⃣ Common Mistakes Self-Employed Individuals Make
• Opening a Solo 401(k) even though they have W-2 employees
• Assuming a SEP IRA has a Roth option (it does not)
• S Corp owners calculating SEP contributions using net earnings instead of W-2 wages
Once you understand how each plan works, the best choice becomes much clearer.
This article is based on 2025 income rules (2026 Filing Season) under U.S. federal tax law.
State tax rules may differ. This content is for general information only and is not individualized tax advice.