Choosing between a SEP IRA and Solo 401(k) can add tens of thousands to your retirement savings. Both plans let self-employed professionals save up to $72,000 annually, but the differences matter more than you think.
The Solo 401(k) typically wins for single business owners who want maximum savings flexibility. The SEP IRA works better if you have employees or want simpler administration. Here’s everything you need to know to make the right choice.
Quick Facts: SEP IRA vs Solo 401(k) Comparison
| Feature | SEP IRA | Solo 401(k) |
|---|---|---|
| Maximum Contribution | $72,000 | $72,000 (under 50) $80,000 (50+) $83,250 (60-63) |
| Contribution Type | Employer only (25% of income) | Employee + Employer |
| Catch-Up Contributions | None | $8,000 (50+) $11,250 (60-63) |
| Setup Complexity | Very simple | Moderate |
| Employees Allowed | Yes (must contribute equally) | Spouse only |
| Loan Options | No | Yes (up to $50,000) |
| Roth Option | Yes (new) | Yes |
| Annual Reporting | None | Form 5500-SF (if balance >$250,000) |
What Is a SEP IRA?
A SEP IRA is a Simplified Employee Pension plan that lets business owners contribute up to 25% of compensation for themselves and employees.
You can contribute up to $72,000 in 2026. The plan works for sole proprietors, partnerships, LLCs, S corporations, and C corporations. You don’t need an established business—freelancers and gig workers qualify too.
SEP IRA Eligibility Requirements
Employees qualify if they:
- Reached age 21
- Worked for you in at least three of the last five years
- Earned at least $800 in compensation (2026 threshold)
How SEP IRA Contributions Work
You (the employer) make all contributions. Employees can’t contribute from their paychecks. For 2026, you can contribute the lesser of $72,000 or 25% of compensation. The compensation cap is $360,000.
If you contribute 10% of your income to your own SEP IRA, you must contribute 10% for every eligible employee. This equal-percentage rule makes SEP IRAs less attractive as your team grows.
You can adjust or skip contributions any year. This flexibility helps businesses with fluctuating income.
SEP IRA Tax Benefits
Contributions are tax-deductible. You deduct up to 25% of compensation (up to the $360,000 cap). For self-employed individuals, deductions are capped at 25% of net self-employment income.
Money grows tax-deferred. You pay taxes when you withdraw in retirement.
What Is a Solo 401(k)?
A Solo 401(k) is a retirement plan for business owners with no employees except a spouse or business partner.
You contribute as both employee and employer. This “double-dipping” lets you save more, faster. For 2026, you can contribute up to $72,000 if you’re under 50, or $80,000 if you’re 50 or older.
Solo 401(k) Eligibility Requirements
You qualify if you:
- Own a business with no full-time employees (except spouse or partner)
- Have self-employment income
- Need an Employer Identification Number (EIN)
A full-time employee works more than 1,000 hours per year. You can hire temporary or seasonal workers below this threshold.
How Solo 401(k) Contributions Work
You make two types of contributions:
Employee Contribution: You contribute up to $24,500 in 2026 (100% of compensation up to this limit). This is your elective deferral.
Employer Contribution: You contribute up to 25% of compensation (20% for sole proprietors). The combined total can’t exceed $72,000.
Catch-Up Contributions: If you’re 50 or older, add $8,000. If you’re 60-63, add $11,250. These bonuses push your maximum to $80,000 or $83,250.
Your spouse can participate and make equal contributions. A married couple can save up to $144,000 (under 50) or $160,000 (50+) annually.
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Solo 401(k) Tax Benefits
Choose traditional (pre-tax) or Roth (after-tax) contributions. Traditional contributions reduce your current taxable income. Roth contributions grow tax-free and you withdraw tax-free in retirement.
Employer contributions reduce your business taxes. Employee contributions reduce your personal income taxes.
SEP IRA vs Solo 401(k): Key Differences
Contribution Limits
Both plans max out at $72,000 for 2026. The Solo 401(k) gets you there faster.
With a SEP IRA, you save 25% of income only. To hit $72,000, you need $288,000 in compensation.
With a Solo 401(k), you can save 100% as an employee up to $24,500, then add employer contributions. You can max out with much lower income.
Catch-Up Contributions
The Solo 401(k) offers catch-up contributions. Add $8,000 at age 50+ or $11,250 at age 60-63. The SEP IRA has no catch-up option.
This difference adds up. Over 10 years, that’s $80,000-$112,500 extra in retirement savings.
Employee Participation
The SEP IRA works if you have employees. You must contribute the same percentage to all eligible employees. If you give yourself 15%, you give everyone 15%.
The Solo 401(k) only works for spouse/partner. Add one full-time employee and you must switch plans.
Contribution Flexibility
The SEP IRA offers more annual flexibility. Skip contributions in bad years. Increase them when profits rise. No minimum contribution required.
The Solo 401(k) requires “substantial and recurring” contributions. You can’t skip years repeatedly without risking plan status.
Loan Options
The Solo 401(k) lets you borrow up to 50% of your balance (maximum $50,000). Useful for emergencies or opportunities. You pay yourself back with interest.
The SEP IRA doesn’t allow loans. Early withdrawals before 59½ trigger a 10% penalty plus income tax.
Administrative Requirements
The SEP IRA wins on simplicity. No annual IRS reporting. Setup takes minutes.
The Solo 401(k) requires Form 5500-SF once your balance exceeds $250,000. This adds paperwork but isn’t burdensome.
SEP IRA vs Solo 401(k) Contribution Examples
Scenario 1: Freelancer Earning $100,000
SEP IRA:
- Maximum contribution: $25,000 (25% of $100,000)
- Tax savings at 24% bracket: $6,000
Solo 401(k):
- Employee contribution: $24,500
- Employer contribution (20% for self-employed): $20,000
- Total: $44,500
- Tax savings at 24% bracket: $10,680
The Solo 401(k) saves an extra $19,500 and reduces taxes by $4,680 more.
Scenario 2: Business Owner with 3 Employees
SEP IRA:
- You contribute 20% for yourself: $20,000
- Must contribute 20% for 3 employees earning $50,000 each: $30,000
- Total business cost: $50,000
Solo 401(k):
- Not eligible with employees
- Must use SEP IRA or other plan
The SEP IRA costs more when you have employees, but it’s your only option.
Which Plan Is Better for You?
Choose the Solo 401(k) If You:
- Run a one-person business or work only with your spouse
- Want to save more than 25% of your income
- Are age 50+ and want catch-up contributions
- Work a regular job and side gig (maximize both plans)
- Want loan options for emergencies
- Prefer Roth contributions for tax-free retirement income
Choose the SEP IRA If You:
- Have employees and want to offer retirement benefits
- Want the simplest possible administration
- Have fluctuating income and need contribution flexibility
- Don’t want to track employee deferrals
- Plan to hire employees soon
- Prefer avoiding annual IRS reporting
Setting Up Your Plan
SEP IRA Setup
- Choose a provider (Fidelity, Schwab, Vanguard)
- Complete IRS Form 5305-SEP or use provider’s version
- Open SEP-IRA accounts for yourself and eligible employees
- Make contributions by your tax filing deadline (including extensions)
No annual fees at major brokers. Setup takes 15-30 minutes.
Solo 401(k) Setup
- Get an EIN if you don’t have one
- Choose a provider (Fidelity, Schwab, E-Trade)
- Complete plan adoption documents
- Open your 401(k) account
- Make contributions by your tax filing deadline (including extensions)
Most providers don’t charge setup fees. Some charge annual maintenance fees once your balance exceeds certain thresholds.
Can You Have Both Plans?
Yes, but with limits. You can maintain both a SEP IRA and Solo 401(k) if you have multiple businesses. However, your total employee contributions across all 401(k) plans can’t exceed $24,500 (2026).
Employer contributions are calculated separately for each business. You can maximize employer contributions in each plan up to the $72,000 total limit per business.
Tax Implications and Withdrawal Rules
Contribution Deadlines
Both plans: Contributions must be made by your business tax filing deadline, including extensions. For most self-employed individuals, this means up to October 15.
Withdrawal Rules
You can start penalty-free withdrawals at age 59½. Early withdrawals trigger a 10% penalty plus income tax (unless you qualify for exceptions).
Required Minimum Distributions (RMDs) begin at age 73. You must withdraw a calculated percentage each year or face a 50% penalty on the amount not withdrawn.
Roth accounts follow different rules. Qualified distributions are tax-free and penalty-free after age 59½ and five years of account ownership.
Common Mistakes to Avoid
Mistake 1: Not Contributing Enough
Many self-employed people underutilize these plans. The high contribution limits are your biggest tax break. Maximize contributions when possible.
Mistake 2: Missing Deadlines
Contributions must be made by your tax filing deadline. Missing the deadline means missing the deduction and contribution for that year.
Mistake 3: Incorrect Contribution Calculations
Self-employed calculations are tricky. For sole proprietors, you calculate based on net self-employment income after deducting half of self-employment tax. Use IRS worksheets or consult a tax professional.
Mistake 4: Not Planning for Employees
Choose a Solo 401(k) and hire your first employee? You can’t contribute anymore. Plan ahead if you anticipate hiring.
Mistake 5: Forgetting State Tax Benefits
Most states follow federal rules and allow deductions for retirement contributions. Check your state’s specific rules for maximum savings.
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Solo 401(k) vs SEP IRA Investment Options
Both plans offer similar investment flexibility:
- Stocks and ETFs
- Mutual funds
- Bonds
- Index funds
- REITs
- CDs and money market funds
Some providers offer self-directed options for alternative investments like real estate or private placements. These require additional documentation and compliance.
Neither plan limits you to employer-sponsored investment options. You control your investment choices, unlike traditional 401(k) plans.
The Bottom Line
The Solo 401(k) is better for most self-employed individuals without employees. You save more, faster, with catch-up options and loan features. The employee contribution flexibility lets you max out contributions even with moderate income.
The SEP IRA wins if you have employees or want maximum simplicity. The equal-percentage rule creates fairness for your team. Zero reporting requirements keep administration simple.
Both plans offer identical investment options and similar contribution limits. The decision comes down to your business structure, employee situation, and age.
Most self-employed professionals should start with a Solo 401(k) and switch to a SEP IRA only when they hire employees.
Frequently Asked Questions
Can I convert my SEP IRA to a Solo 401(k)?
You can’t directly convert a SEP IRA to a Solo 401(k). However, you can roll over SEP IRA funds to a Solo 401(k) if your Solo 401(k) plan allows incoming rollovers. Check with your plan provider first. You can also maintain both accounts separately going forward.
What happens to my Solo 401(k) if I hire an employee?
You must either terminate the Solo 401(k) and set up a different plan (like a SEP IRA or traditional 401(k)) or exclude new employees from the plan for one year. Once an employee is eligible, the Solo 401(k) structure no longer works. Plan ahead before hiring to avoid complications.
Can I contribute to both a workplace 401(k) and a Solo 401(k)?
Yes, but your total employee contributions across all 401(k) plans can’t exceed $24,500 (2026). If you max out your workplace 401(k), you can still make employer contributions to your Solo 401(k) based on your self-employment income. This strategy lets high earners save even more.
Which plan offers better creditor protection?
Both plans offer strong creditor protection under ERISA and bankruptcy laws. Solo 401(k) plans typically offer stronger protection because they’re covered by ERISA. SEP IRAs have federal protection up to $1,512,350 in bankruptcy (2024 threshold, adjusted periodically). State laws may provide additional protection for both plan types.
Can I have a Roth option with both plans?
Yes. Both SEP IRAs and Solo 401(k) plans now offer Roth options. With a Solo 401(k), you can split contributions between traditional and Roth. For SEP IRAs, Roth contributions are a newer option (added under SECURE Act 2.0), so check if your provider offers this feature. Roth contributions don’t reduce current taxes but provide tax-free retirement income.