Solo 401(k) vs SEP IRA: Which Retirement Plan Saves Freelancers More Money?

Choosing the right retirement plan can save you thousands in taxes and build real wealth over your freelance career. Both the Solo 401(k) and SEP IRA are popular choices for self-employed workers, but they differ significantly in contribution limits, flexibility, loan options, and paperwork. This guide breaks down the mechanics, costs, and real-world math so you can pick the plan that maximizes your retirement savings in 2026.

Key Takeaways

• Solo 401(k)s allow higher total contributions (up to $69,000 in 2026 for workers under 50) because you contribute as both employee and employer.
• SEP IRAs are simpler to set up and maintain, with no annual filing requirements and minimal paperwork.
• Solo 401(k)s offer Roth contributions and loan options; SEP IRAs do not.
• If you have employees, a SEP IRA may become expensive because you must contribute the same percentage to all eligible workers.
• Choose a Solo 401(k) if you want to maximize contributions or need a loan option; pick a SEP IRA if you value simplicity and have fluctuating income.

How does a Solo 401(k) work?

A Solo 401(k)—also called an Individual 401(k) or one-participant 401(k)—functions like a traditional employer-sponsored 401(k), but it's designed for self-employed people with no full-time employees (other than a spouse). You wear two hats: employee and employer.

As the employee, you can defer up to $23,000 of your net self-employment income in 2026 (or $30,500 if you're 50 or older, thanks to the catch-up contribution). This portion can be traditional (pre-tax) or Roth (after-tax).

As the employer, you can contribute up to 25% of your W-2 compensation (if you pay yourself a salary through an S corp) or roughly 20% of your net self-employment earnings (after deducting half of self-employment tax) if you're a sole proprietor or single-member LLC.

Combined, your total contributions from both sides cannot exceed $69,000 in 2026 ($76,500 if age 50+), according to IRS Publication 560.

Solo 401(k) loan feature

Unlike a SEP IRA, a Solo 401(k) lets you borrow up to $50,000 or 50% of your vested account balance (whichever is less) and repay yourself with interest. This can be a lifeline in emergencies, but treat it carefully—defaulting converts the loan into a taxable distribution.

How does a SEP IRA work?

A SEP IRA (Simplified Employee Pension Individual Retirement Account) is even simpler. Only the employer makes contributions—there is no employee deferral component. You contribute up to 25% of your W-2 compensation or roughly 20% of net self-employment income (after the SE tax deduction), with a maximum contribution of $69,000 in 2026, per the IRS.

Because there's no employee deferral, a SEP IRA is particularly attractive if your income fluctuates year to year. You're not locked into contributing a fixed dollar amount; you can adjust the percentage each year—or skip it entirely if cash flow is tight.

SEP IRAs also have minimal setup and maintenance. You don't file Form 5500 (the annual report required for many 401(k) plans once assets exceed $250,000). Most brokerages let you open a SEP IRA in minutes online with no setup fees.

Side-by-side comparison: Solo 401(k) vs SEP IRA

Real-world example: Solo 401(k) vs SEP IRA contribution

Scenario: You're a 40-year-old freelance graphic designer operating as a sole proprietor. In 2026, you earn $100,000 in net profit from Schedule C.

Step 1: Deduct half of self-employment tax

Self-employment tax is 15.3% on 92.35% of net earnings.

• SE tax = $100,000 × 0.9235 × 0.153 = $14,130
• Deduction = $14,130 ÷ 2 = $7,065
• Adjusted net earnings = $100,000 – $7,065 = $92,935

Step 2: Calculate employer contribution

For sole proprietors, the effective rate is roughly 18.587% of adjusted net earnings (the IRS uses 20% of net SE income after the deduction, which works out to this figure).

• Employer contribution = $92,935 × 0.18587 ≈ $17,275

SEP IRA total contribution

• $17,275 (employer only)

Solo 401(k) total contribution

• Employee deferral: $23,000
• Employer contribution: $17,275
• Total: $40,275

Result: The Solo 401(k) lets you contribute $22,000 more in this scenario, cutting your 2026 taxable income by an extra $22,000.

Which plan is right for you?

Choose a Solo 401(k) if you:

• Want to maximize contributions, especially if your net income is below $120,000 (where the employee deferral matters most).
• Want the flexibility of Roth contributions to diversify your tax treatment in retirement.
• Might need to borrow from your retirement account in an emergency.
• Are comfortable with slightly more paperwork and potential Form 5500 filings once your balance exceeds $250,000.

Choose a SEP IRA if you:

• Have highly variable income and want the option to skip contributions in lean years.
• Want the simplest possible setup—no trust documents, no annual filings.
• Are over 50 but your income is high enough that the employer-side contribution alone maxes you out anyway (diminishing the catch-up advantage).
• Plan to hire W-2 employees in the near future and want to avoid complicated 401(k) nondiscrimination testing (though note: you'll still owe the same SEP contribution percentage to all eligible employees).

What if you have employees?

This is where the two plans diverge sharply.

SEP IRA: You must contribute the same percentage of compensation for every eligible employee (generally anyone 21+ who earned at least $750 in 2026 and worked for you in three of the last five years). If you contribute 20% for yourself, you owe 20% for each eligible worker.

Solo 401(k): Technically, you can only use a Solo 401(k) if you have no full-time employees other than your spouse. If you hire a part-time or contract worker who later becomes a common-law employee, you may need to convert to a standard 401(k) or switch to a SEP IRA.

Bottom line: if you're truly solo (or working only with your spouse), the Solo 401(k) is usually the better deal. If you anticipate hiring, plan accordingly.

Common mistakes to avoid

Opening both a Solo 401(k) and a SEP IRA in the same year. The IRS aggregates contributions across all employer plans, so your combined limit is still $69,000 ($76,500 age 50+). You won't double your contribution room; you'll just add administrative headaches.

Missing the contribution deadline. For both plans, you can make employer contributions up until your tax-filing deadline plus extensions (typically October 15 of the following year if you file Form 4868). Employee deferrals for a Solo 401(k), however, must be made by December 31 of the tax year.

Forgetting Form 5500-EZ. If your Solo 401(k) balance exceeds $250,000 at year-end, you must file Form 5500-EZ by July 31 of the following year. The penalty for missing this filing is $250 per day (up to $150,000), according to the Department of Labor.

Not updating beneficiaries. Retirement accounts pass by beneficiary designation, not your will. Log in and confirm your beneficiaries are current—especially after major life events like marriage, divorce, or the birth of a child.

Mixing personal and business finances. Both SEP IRAs and Solo 401(k)s require a separate retirement account. Never commingle these funds with your operating account or personal savings.

How to set up each plan

Solo 401(k) setup checklist

1. Obtain an EIN for the plan (even if you already have one for your business).
2. Adopt a written plan document. Many brokerages (Fidelity, Vanguard, E*TRADE, Charles Schwab) offer free prototype plans.
3. Open the Solo 401(k) brokerage account and link your business checking account.
4. Make employee deferrals by December 31 and employer contributions by your tax deadline (plus extensions).
5. File Form 5500-EZ if your plan assets exceed $250,000.

SEP IRA setup checklist

1. Complete IRS Form 5305-SEP (or use your brokerage's version) to establish the plan.
2. Open a SEP IRA account at your chosen brokerage.
3. Make contributions by your tax-filing deadline (including extensions).
4. Provide each eligible employee with a copy of the SEP agreement and set up their SEP IRA accounts if you have staff.

Most freelancers can complete SEP IRA setup in under 30 minutes online with no fees.

Conclusion and next steps

For most solo freelancers earning under $120,000, the Solo 401(k) delivers higher contribution limits and more flexibility—especially if you want Roth options or a loan feature. If you value simplicity, have fluctuating income, or want to avoid annual filings, the SEP IRA is an excellent low-maintenance choice. Either plan offers powerful tax deductions and long-term wealth building. Run the numbers with your specific income using our Self-Employment Tax Calculator, compare setup costs at your preferred brokerage, and consider booking a consultation with a CPA to confirm which plan fits your business structure and retirement goals.

Related guides

• SEP IRA Guide for Freelancers: How to Save Big for Retirement in 2026
• Tax Extensions for Freelancers: How to File for More Time
• Freelancer vs Independent Contractor: What's the Difference?
• Self-Employment Tax Explained: The 15.3% You Can't Avoid
• 1099-NEC vs 1099-MISC: What's the Difference and Which One You'll Get

Run the numbers

• Self-Employment Tax Calculator