SEP-IRA vs. Solo 401(k): Which Retirement Account Is Better for Self-Employed?

Quick Answer

Solo 401(k) is better for most self-employed people because it allows higher contributions at lower income levels and offers a Roth option. SEP-IRA is simpler to set up and administer. On $100,000 net self-employment income, a Solo 401(k) allows $47,000 vs. $18,600 for a SEP-IRA. At very high income ($200,000+), both max out similarly at $70,000 (2026 limit).

2026 Contribution Limits

Solo 401(k)

A Solo 401(k) has two contribution buckets:

Employee contribution (elective deferral): Up to $23,500 in 2026 ($31,000 if age 50+)

• Can be traditional (pre-tax) or Roth (post-tax)
• Not tied to your income above a threshold

Employer contribution (profit sharing): Up to 25% of W-2 wages (S-Corp) or 20% of net self-employment income (sole prop/LLC)

• Pre-tax only
• Cannot exceed $46,500

Combined maximum: $70,000 (under 50) or $77,500 (50+ catch-up) in 2026

SEP-IRA

Contribution: Up to 25% of W-2 wages (S-Corp) or 20% of net self-employment income (sole prop/LLC)

• Pre-tax only (no Roth option)
• Same maximum: $70,000

Note: SEP-IRA has no employee deferral component—only employer contributions. This is why it maxes out later as income rises.

Head-to-Head Comparison by Income Level

$60,000 Net Self-Employment Income

Solo 401(k) advantage: $23,500 more in contributions at $60K income

$100,000 Net Self-Employment Income

Solo 401(k) advantage: $23,500 more

$200,000 Net Self-Employment Income

Solo 401(k) advantage: Still $23,500 more (until employer contribution hits max)

$350,000+ Net Self-Employment Income

Both accounts can reach the $70,000 maximum. At this income level, the SEP-IRA and Solo 401(k) employer contributions both max out at $70,000. The only remaining differences are structure, Roth option, and loan provisions.

Use smallbiz-retirement-sep-solo-401k-calculator to calculate your exact contributions at any income level.

The Roth Solo 401(k): A Major Differentiator

The Solo 401(k) employee deferral can be contributed as Roth (after-tax). SEP-IRAs have no Roth option.

Why Roth matters for self-employed:

Income limits don't apply. Regular Roth IRA contributions phase out at $150,000 (single) or $236,000 (married) in 2026. Roth 401(k) contributions have NO income limit.

Tax-free growth forever. Roth contributions grow tax-free and are withdrawn tax-free in retirement. This is especially valuable for young high-earners who expect to be in a higher bracket later.

Mega backdoor Roth potential. Some Solo 401(k) plans allow after-tax contributions above the employee limit, which can then be converted to Roth—potentially sheltering $40,000+ annually in Roth accounts.

SEP-IRA Advantages

Simplicity

Setting up a SEP-IRA takes 15 minutes. Open at Vanguard, Fidelity, or Schwab online. No annual IRS filing (unlike Solo 401(k) that requires Form 5500 once assets exceed $250,000). No plan documents required. Contribute up to tax filing deadline (including extensions).

Best for: Side hustles, variable income situations, or anyone who values simplicity over maximum contribution flexibility.

Contribution Deadline Flexibility

Both accounts allow contributions up to the tax filing deadline (April 15 + extensions to October 15). This means you can determine your exact contribution after knowing your full-year income—valuable for variable-income businesses.

Multi-Employee Businesses

If you have W-2 employees (not just yourself), SEP-IRA contributions must be made for all eligible employees at the same percentage as your own contribution. This can make SEP-IRA very expensive if you have employees.

Solo 401(k) is only available to owner-employees with no W-2 employees (except a spouse).

Solo 401(k) Advantages

Higher Contributions at Lower Income

The employee deferral component means you can contribute significantly more than 20% of net income at lower income levels. This is the primary advantage for most self-employed people.

Roth Option

As noted above, tax-free retirement savings with no income limit.

Loan Provisions

Solo 401(k) plans can allow participant loans (up to 50% of vested balance or $50,000, whichever is less). Some plans include this feature; others don't. SEP-IRAs are IRAs and cannot be borrowed against without triggering a distribution.

Spousal Inclusion

If your spouse works in the business, they can also contribute to the Solo 401(k) as an employee, potentially doubling household contributions.

Common Mistakes (Do This, Not That)

❌ Mistake 1: Defaulting to SEP-IRA because it's simpler without calculating the contribution difference At $100,000 income, you're leaving $23,500 in annual tax-deferred contributions on the table by choosing SEP-IRA over Solo 401(k). That's $5,170 in immediate tax savings for a 22% bracket earner—compounding over decades.

✅ Do this: Calculate your actual contribution difference using smallbiz-retirement-sep-solo-401k-calculator. The Solo 401(k) setup takes only a few hours; the extra contributions are worth it for most self-employed earners under $350,000.

❌ Mistake 2: Hiring an employee and not realizing it disqualifies your Solo 401(k) If you hire your first W-2 employee (other than your spouse), your Solo 401(k) eligibility ends. You must either amend to a full 401(k) plan (for employees) or switch to SEP-IRA.

✅ Do this: Plan ahead. If you might hire employees in 2–3 years, either set up a traditional 401(k) plan now that can accommodate employees, or be prepared to transition when the time comes.

❌ Mistake 3: Not contributing to retirement because income is "too low" "I only made $40,000 this year—I can't afford retirement." With a Solo 401(k), you can contribute $23,500 as an employee deferral even on $40,000 income. The tax savings at 22% bracket = $5,170 refund—effectively making the $23,500 contribution cost only $18,330 out of pocket.

✅ Do this: Always contribute at least enough to maximize your tax savings. Use retirement-calculator to see the long-term impact of starting contributions now.

Step-by-Step Account Selection Checklist

• Determine your net self-employment income for the year
• Check: Do you have W-2 employees (other than spouse)? If yes → SEP-IRA only (or full 401k plan)
• Calculate Solo 401(k) contributions: $23,500 employee + 20% × net income
• Calculate SEP-IRA contributions: 20% × net income
• If income < $350,000: Solo 401(k) allows significantly more contributions
• If you want Roth contributions: Solo 401(k) required (SEP has no Roth option)
• If income > $350,000: Both max out similarly; choose based on simplicity vs. Roth desire
• Open Solo 401(k) before December 31 of the tax year (SEP-IRA can be opened by tax deadline)
• Make employee contributions by December 31 (employer contributions by tax deadline)
• Track Form 5500-EZ requirement: file when Solo 401(k) assets exceed $250,000

Frequently Asked Questions

Q: Can I have both a SEP-IRA and a Solo 401(k)? A: Yes, but your total contributions across all employer plans are capped at the annual limit ($70,000). If you have both, contributions to each count toward the combined limit. There's generally no benefit to having both.

Q: Can I make a SEP-IRA contribution for a past year? A: Yes, up to the tax filing deadline including extensions (October 15). This is a major flexibility advantage—you can determine your optimal contribution after seeing the full year's income.

Q: What happens to my Solo 401(k) if I incorporate? A: When you form an S-Corp, your compensation basis changes from net self-employment income to W-2 wages. Update your plan accordingly. Employee contributions remain unchanged; employer contributions shift to 25% of W-2 wages.

Q: Where should I open a Solo 401(k)? A: Fidelity (Fidelity Self-Employed 401(k)) and Vanguard (Individual 401(k)) offer low-cost Solo 401(k) plans. Fidelity allows both traditional and Roth contributions with no annual fees. Schwab offers a similar option. Avoid high-fee insurance-based plans.

Q: What's the deadline to establish a Solo 401(k)? A: Must be established by December 31 of the tax year (not the filing deadline, unlike SEP-IRA). Plan ahead—some custodians need 2–3 weeks to process new plan applications.

Related Tools

• SEP-IRA vs. Solo 401(k) Calculator — Calculate exact contributions and tax savings for your income level
• Self-Employment Tax Calculator — Model your complete self-employment tax burden
• Retirement Calculator — Project your retirement savings with consistent contributions