By Income Tax Service Editorial — Reviewed by Diyan Yap, EA (IRS Enrolled Agent) — Updated August 10, 2026
Quick answer: Both plans stop at the same $72,000 annual-additions ceiling for 2026, but they get there differently. A SEP IRA is employer-only, limited to 25% of compensation. A solo 401(k) adds an employee deferral of up to $24,500 on top of that employer contribution, so it usually allows a much larger deduction at moderate income levels.
Key facts:
- SEP IRA 2026: employer-only contributions up to the lesser of 25% of compensation or $72,000
- Solo 401(k) 2026: combined employee + employer limit of $72,000 under age 50, higher with age-based catch-up
- Solo 401(k) employee deferral for 2026: up to $24,500, plus $8,000 catch-up at age 50+
- SIMPLE IRA 2026: $17,000 employee deferral, employer match up to 3% of pay or a 2% non-elective contribution, for employers with 100 or fewer employees
- SEP contribution percentages must be uniform across all eligible employees
- SEP is the easiest plan to administer for a solo owner with no staff
The two plans are often presented as interchangeable. They are not. At the same income, a solo 401(k) frequently allows twice the contribution — and the reason is structural, not a matter of provider or paperwork.
How does each plan work?
A SEP IRA is funded entirely by the employer. There is no employee deferral, so the whole contribution is a percentage of compensation, capped at 25%, and it must be applied uniformly to every eligible employee. That uniformity is what makes SEPs simple for a one-person business and expensive for a business with staff.
A solo 401(k) is a one-participant 401(k) plan for a business with no employees other than the owner (and a spouse). It has two contribution sources: an employee elective deferral out of your own compensation, plus an employer contribution — and both land in the same account, subject to one overall ceiling.
A SIMPLE IRA is the third option and a different animal: employee deferrals up to $17,000 for 2026 with a required employer match up to 3% of compensation or a 2% non-elective contribution, available only to employers with 100 or fewer employees. It’s built for small businesses with staff who want low administration, not for maximizing an owner’s own deduction.
| Feature | SEP IRA | Solo 401(k) | SIMPLE IRA |
|---|---|---|---|
| Who contributes | Employer only | Employee deferral + employer | Employee deferral + required employer contribution |
| 2026 ceiling | Lesser of 25% of compensation or $72,000 | $72,000 under 50; higher with catch-up | $17,000 deferral plus employer match |
| Employee deferral | None | Up to $24,500 (plus $8,000 at 50+) | Up to $17,000 |
| Employees allowed | Yes, but contributions must be uniform | Owner and spouse only | Up to 100 employees |
| Administration | Easiest | Moderate; plan document required | Low |
| Plan loans | Not permitted | Permitted if the plan document allows | Not permitted |
Which plan allows a bigger contribution at $80,000? (worked example)
The solo 401(k), by a wide margin — because the employee deferral stacks on top of the same employer percentage the SEP is limited to.
Assume $80,000 of compensation and an owner under age 50:
- SEP IRA: 25% × $80,000 = $20,000 total
- Solo 401(k): $24,500 employee deferral + 25% × $80,000 = $20,000 employer contribution = $44,500 total, well under the $72,000 ceiling
- Difference: $24,500 of additional deductible retirement savings, from the same income
- At age 50+, the solo 401(k) adds the $8,000 catch-up, reaching $52,500
One important caveat on the arithmetic: for an unincorporated sole proprietor, the employer contribution is calculated on net earnings after required self-employment adjustments rather than on gross profit, so the real employer number lands below a flat 25% of net profit. The comparison and the ranking hold — the solo 401(k) still wins — but have the exact figure computed for your entity type rather than assuming 25% of your Schedule C bottom line.
At what income do SEP and solo 401(k) converge?
Around $288,000 of compensation, because that is where 25% alone reaches the shared $72,000 ceiling: 25% × $288,000 = $72,000. Above that point both plans cap out at the same number, so the solo 401(k)’s deferral advantage disappears and the decision turns entirely on features.
That gives a clean decision rule:
- Below roughly $288,000 of compensation: the solo 401(k) generally allows a larger contribution, often dramatically so at modest income
- At or above that level: both plans hit $72,000, and you choose on administration, loan access, Roth options, and creditor considerations
- Any income, if you have non-spouse employees: the solo 401(k) is off the table — a SEP or SIMPLE (or a full 401(k) plan) is the conversation
- If you want the absolute simplest setup and the SEP number is already enough, simplicity has real value
Note also that the plans differ on deadlines and paperwork: a 401(k) needs a plan document in place under its own timing rules, while a SEP can typically be established and funded later in the process. If you are reading this late in the year, that timing difference may decide it for you — confirm current deadlines before assuming either is still available for 2026.
Which plan should a self-employed owner choose?
Choose based on staff, income, and how much you actually intend to contribute — in that order.
- Do you have non-spouse employees? If yes, the solo 401(k) is out. A SEP works but forces uniform percentages for everyone; a SIMPLE caps your own deferral at $17,000 but spreads cost more predictably.
- How much do you want to put away? If your target is under 25% of compensation, the SEP’s simplicity may be worth more than the solo 401(k)’s headroom.
- Is your income near $288,000 or above? Then both reach $72,000 and you’re choosing on features.
- Do you want loan access or Roth contributions inside the plan? Those generally point to the 401(k) side.
Entity structure interacts with all of this, because “compensation” means W-2 wages for an S-corp owner and net earnings for a sole proprietor — and the wage level is itself a decision. Our S-corp vs LLC guide covers how a salary choice ripples into retirement contribution capacity, and the full 2026 contribution limits list the figures for every account type.
What should you do now?
- Compute your actual compensation base for retirement purposes — it is not simply your revenue or your Schedule C profit.
- Set a savings target first, then pick the plan that reaches it with the least complexity.
- Check the deadlines this year, since plan-establishment timing differs between a 401(k) and a SEP.
- Coordinate with your salary decision if you run an S corporation; the wage level caps the employer contribution.
- Plan the cash flow. Large contributions change your quarterly estimated payments — better to adjust during the year than to be short in April.
- Get one comparison run on your real numbers. A credentialed tax professional (like an IRS Enrolled Agent) can produce side-by-side contribution figures and the resulting tax savings in a single session.
FAQ
Can I contribute more to a solo 401(k) than a SEP IRA?
Usually yes, at moderate income. Both share a $72,000 ceiling for 2026, but the solo 401(k) adds an employee deferral of up to $24,500 on top of the employer contribution.
Can I have a solo 401(k) if I have employees?
No. A solo 401(k) is limited to a business with no employees other than the owner and a spouse. With staff, look at a SEP, a SIMPLE, or a conventional 401(k).
What is the 2026 SEP IRA contribution limit?
The lesser of 25% of compensation or $72,000.
Does a SEP IRA require me to contribute the same percentage for employees?
Yes. The contribution percentage must be uniform across all eligible employees, which is what makes SEPs expensive once you have staff.
Can I borrow from either plan?
A solo 401(k) may permit loans if the plan document allows it. SEP and SIMPLE IRAs cannot make loans.
Is a SIMPLE IRA better than a SEP for a one-person business?
Usually not for maximizing your own contribution — the SIMPLE deferral limit is $17,000 for 2026, while a SEP can reach 25% of compensation up to $72,000. SIMPLE plans are designed for small businesses with employees.
Sources
- IRS: 401(k) limit increases to $24,500 for 2026, IRA limit increases to $7,500
- IRS Notice 2025-67 (primary source)
- IRS: Estimated taxes for small business and self-employed
This article is for educational purposes only and is not tax, legal, or financial advice. Tax rules change and individual situations vary — consult a qualified tax professional about your specific circumstances.