"Self-Employed Retirement: SEP IRA vs. Solo 401(k) vs. Defined Benefit Plans"

The dirty secret of self-employment taxation: yes, you owe both halves of Social Security and Medicare (~15.3% combined). Yes, quarterly estimated taxes are a pain. But self-employed people also have access to the most powerful retirement accounts in the tax code — accounts that dwarf what W-2 employees can contribute. A freelance designer earning $150,000 can shelter more in retirement accounts than a W-2 VP making the same money, and it's not close.

Three main vehicles to know: SEP IRA, Solo 401(k), and Defined Benefit plans. Each has different mechanics, contribution limits, complexity, and best-use scenarios. Getting this right is one of the highest-leverage tax moves available to anyone with self-employment income — freelancers, consultants, small business owners, 1099 contractors, side hustle earners, anyone operating as a sole prop, LLC, S-corp, or partnership.

Let me walk through each.

What Is a SEP IRA and Who Is It Best For?

A SEP IRA (Simplified Employee Pension) is the most straightforward self-employed retirement account. It's essentially a traditional IRA on steroids — easy to open, simple to contribute to, with dramatically higher limits.

2026 contribution rules:

• Contribution limit: up to 25% of net self-employment income (or 20% of gross SE income after deducting half of SE tax), with a hard cap of $72,000 for 2026.
• Compensation used for the calc: first $360,000 of compensation for 2026.
• Eligibility threshold: any employee earning at least $800 in 2026 (relevant if you have employees; for yourself, any earned income qualifies).
• Tax treatment: contributions are tax-deductible (reduce this year's taxable income); earnings grow tax-deferred; withdrawals in retirement are taxed as ordinary income.

Why it's attractive:

• Extremely easy setup. Open in an afternoon at Fidelity, Schwab, Vanguard, or any major brokerage. No Form 5500 filing regardless of balance.
• Flexible contributions year-to-year. Big income year? Max it. Slow year? Contribute less or skip entirely. No required minimum.
• Can fund until your tax deadline (including extensions). A SEP for tax year 2026 can be funded as late as October 15, 2027 if you filed an extension. Massive flexibility.

Why it's limited:

• No Roth option (mostly). Traditional SEP contributions only — so you get the upfront deduction but pay tax on withdrawal. SECURE 2.0 authorized Roth SEP IRAs, but adoption by custodians has been slow and many brokerages still don't offer them.
• No catch-up contributions. Unlike 401(k)s, SEPs have no over-50 catch-up.
• If you have employees, you must contribute the same percentage for them. Contribute 20% for yourself, you owe 20% of each eligible employee's compensation. For solo operators, irrelevant. For small business owners with staff, expensive.
• Pro-rata rule for Backdoor Roth. SEP balances count toward the pro-rata calculation if you're also running a Backdoor Roth IRA. This can meaningfully reduce the benefit of both strategies. See the high-earner Roth playbook for mechanics.

Best for: solo operators with variable income who want maximum simplicity, no employees, and are comfortable with traditional (pre-tax) contributions only.

What Is a Solo 401(k) and When Does It Beat a SEP?

A Solo 401(k) is a one-participant 401(k) plan designed for self-employed individuals with no employees other than a spouse. It has the same mechanics as a regular 401(k) — including Roth, loans, and pro-rata-friendly structure — but tailored for a single participant.

2026 contribution rules:

• Employee deferral: up to $24,500 (same as regular 401(k) limit).
• Catch-up (age 50+): additional $8,000.
• Super catch-up (ages 60-63, SECURE 2.0): additional $11,250.
• Employer contribution: up to 25% of net SE income (or 20% of gross SE income after half SE tax deduction).
• Total combined limit: $72,000 for 2026 ($80,000 if 50+; $83,250 for ages 60-63).

So at $150,000 of net SE income, you could potentially contribute:

• $24,500 as employee deferral
• Plus ~$30,000 as employer contribution (20% of $150K)
• Total: ~$54,500

Why it beats a SEP for most self-employed individuals:

1. Higher total limits at lower income levels. Because you get both the employee deferral AND the employer contribution, a Solo 401(k) lets you shelter more at income levels below ~$350K. Above that threshold, both plans cap out at $72K. Below, the 401(k) structure wins.

2. Roth option available. Most Solo 401(k) providers allow Roth contributions on the employee deferral portion. Employer contributions are still pre-tax, but you can get up to $24,500 into Roth each year — or $32,500 with catch-up — instead of being limited to a $7,500 Backdoor Roth IRA.

3. Avoids pro-rata problems with Backdoor Roth. Solo 401(k) balances don't count in the Backdoor Roth pro-rata calculation. This lets you run both strategies cleanly.

4. Loan feature. You can borrow from a Solo 401(k) (up to 50% of balance, max $50,000). Useful flexibility in emergencies, though I'd never recommend it as a routine tool.

Why it's more complex than a SEP:

• Form 5500-EZ filing required when plan assets exceed $250,000. Annual filing, not hard, but a real administrative step. Below $250K, no filing required.
• Plan documents and setup fees. Some providers (Fidelity, Schwab, E*TRADE) offer free Solo 401(k)s. Others charge setup and annual fees. Shop around.
• December 31 deadline to establish for current tax year. Unlike SEP which you can set up through October of the following year, a Solo 401(k) generally must be open by year-end. (Technically there's an exception under SECURE 2.0 allowing employer-only contributions to be set up post-year-end, but employee deferrals still require the plan to exist during the year.)

Best for: solo operators who want Roth access, higher contributions at lower income levels, or plan to also run a Backdoor Roth IRA. Also excellent if your spouse works in the business — they can participate separately and double the household's total contribution capacity.

How Does a Defined Benefit Plan Work, and Who Should Use It?

A Defined Benefit (DB) plan is an old-school pension — you define a target retirement benefit, and an actuary calculates how much needs to be contributed each year to fund it. The contribution limits are dramatically higher than SEP or Solo 401(k), but complexity and cost are dramatically higher too.

2026 rules:

• Maximum annual benefit: up to $290,000/year in retirement (Section 415(b) limit for 2026, up from $280,000 in 2025).
• Annual contribution: calculated by an actuary based on your age, income, and target retirement benefit. Typical range: $100,000-$300,000+/year for high-income self-employed individuals in their 40s-60s.
• The older you are, the higher you can contribute. Because you have fewer years to fund the pension target, annual contributions to reach the same benefit are much larger.

Why it's the ultimate shelter for high-income self-employed:

A 55-year-old solo consultant earning $500K/year, with no employees, can potentially contribute $200,000+/year to a DB plan — on top of a Solo 401(k). That's ~$270,000 of tax-deductible retirement savings in a single year. For someone facing a ~40% federal-plus-state marginal rate, the annual tax savings alone run $100K+.

Why most self-employed people shouldn't use one:

• Actuarial costs: $1,500-$3,000/year to maintain, minimum, for the actuarial calculations required to fund the plan.
• Contribution inflexibility: unlike SEP or Solo 401(k), DB contributions are required each year based on the actuarial schedule. A down income year doesn't let you skip — and underfunding triggers penalties.
• Setup complexity: requires a plan document, third-party administrator (TPA), and ongoing compliance filings. Form 5500 required regardless of asset level.
• Works best with stable, high income. Variable-income freelancers face real risk of being unable to meet required contributions in down years.

Who should consider it: solo operators or very small businesses (ideally no rank-and-file employees) with consistent income in the $250K+ range who want to shelter substantially more than SEP or Solo 401(k) limits allow. Usually combined with a Solo 401(k) for maximum effect.

If you're earning $75K-$200K as a freelancer, skip DB plans. The complexity and required contributions outweigh the benefit. If you're a high-earning solo practitioner (attorney, doctor, consultant, successful freelance specialist) with stable $300K+ income and you've already maxed SEP or Solo 401(k) — DB becomes genuinely interesting.

Can You Combine These Accounts?

Yes, with rules. The interplay matters more than people realize.

SEP + Solo 401(k) same business: generally not compatible. You can have both, but the $72,000 total limit applies across both plans. For the same business, you're typically better off picking one — and Solo 401(k) usually wins. The exception: if you have separate unrelated businesses, each can potentially have its own retirement plan.

Solo 401(k) + traditional/Roth IRA + Backdoor Roth: fully compatible. A solo entrepreneur can contribute $24,500 (Solo 401(k) employee) + up to ~$47,500 (Solo 401(k) employer) + $7,500 (Backdoor Roth IRA) = ~$79,500/year of combined capacity in 2026, assuming sufficient income.

Solo 401(k) + Defined Benefit: commonly combined for high earners. The Solo 401(k) contributions count toward the DB plan's Section 404 combined deduction limit (generally 25% of compensation plus the DB contribution), so running both requires coordination — but doing so unlocks the highest sheltered contributions in the tax code.

Spouse who works in the business: major opportunity. If your spouse is a legitimate employee of your business (actually performing work, paid a real salary, W-2 or K-1), they can participate in the Solo 401(k) independently — effectively doubling the household's total contribution capacity. Same logic applies to SEPs and DB plans. The "employed spouse" structure is one of the most powerful and underused strategies in small business retirement planning.

How Does Business Structure (Sole Prop vs. S-Corp) Affect This?

Your choice of business structure materially affects maximum contributions.

Sole proprietorship or single-member LLC: contribution calculations use net self-employment income (gross income minus business expenses, minus half of self-employment tax). Simple and straightforward.

S-Corporation: the S-corp structure changes the math. You pay yourself a "reasonable salary" via W-2 (subject to payroll taxes), and take additional profits as distributions (not subject to payroll taxes). Retirement plan contributions are based on W-2 wages only, not total company income.

This matters in two directions:

1. Lower payroll taxes: setting a lower W-2 salary and taking more as distributions saves ~15.3% in FICA/Medicare on the distribution portion — but this is an IRS scrutiny point (the salary must be "reasonable").

2. Lower retirement plan contribution base: a lower W-2 salary also reduces the max employer contribution to your Solo 401(k) or SEP. So the payroll tax savings has to be balanced against reduced retirement contribution capacity.

The "reasonable salary" tension is one of the most-litigated issues in S-corp taxation. The IRS has attacked S-corp owners who paid themselves, say, $40K salary + $300K distribution when the industry norm for comparable work is $150K+. Work with a CPA who handles S-corps regularly — this structure saves serious money when done correctly and triggers serious penalties when done wrong.

For a full decision framework on freelancer taxes beyond retirement accounts, see how freelancers and side hustlers should handle taxes.

What's the Decision Framework?

For most self-employed readers, here's the priority order:

If you earn <$50K of self-employment income:

• Fund a Roth IRA ($7,500 direct if under the income threshold).
• Optional: open a Solo 401(k) for the Roth option + employer contribution flexibility, but keep contributions modest.

If you earn $50K-$150K:

• Solo 401(k) is almost always the right choice. Employee deferral up to $24,500 + employer match. Roth deferral option if you want tax diversification.
• If simplicity matters more than optimization: SEP IRA works too, especially for the first year or two when you're still figuring out your income rhythm.

If you earn $150K-$350K:

• Solo 401(k) + Backdoor Roth IRA. Max both if possible.
• Roth deferral on some of the Solo 401(k) employee portion — you're in a high bracket now but uncertain about the future.

If you earn $350K+:

• Solo 401(k) + Backdoor Roth + Defined Benefit plan. The DB plan adds six-figure sheltered contributions on top.
• Plus any Mega Backdoor Roth capacity if you have a traditional W-2 job with a plan that supports it.

At every level, if your spouse works in the business legitimately, add their separate retirement plan contributions — doubling the household's tax-advantaged space.

What's the Bottom Line?

If you're self-employed and only using a Traditional IRA, you're leaving the biggest retirement account benefits in the tax code on the table. The SEP IRA lets you shelter up to $72,000/year. The Solo 401(k) does the same with Roth access and better Backdoor Roth compatibility. Defined Benefit plans unlock six-figure annual contributions for the right high-income candidates.

For most self-employed readers, the answer is Solo 401(k), opened by December 31, with Roth deferral toggled on if you want tax diversification. It's the best combination of contribution capacity, Roth access, and long-run flexibility. Fidelity, Schwab, and E*TRADE all offer free Solo 401(k) accounts — no reason to delay.

High earners should add a Backdoor Roth IRA ($7,500 for 2026, or $8,600 if 50+). Very high earners with stable income should evaluate a DB plan with a qualified TPA.

Self-employment is hard. The retirement accounts available to self-employed people are one of the few places where the tax code genuinely rewards the trade-off. Use them.

For the broader picture on your tax-advantaged options, see tax-advantaged accounts explained and the Tax-Advantaged Accounts Cheat Sheet.

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