Solo 401k vs SEP-IRA: Which Is Better for the Self-Employed?
Last reviewed: July 2026
For self-employed business owners comparing the solo 401k vs SEP-IRA self-employed options, the solo 401(k) almost always allows more in annual contributions at the income levels where most independent professionals actually operate. Both plans share the same 2026 annual limit of $72,000 — but the path to that ceiling is entirely different, and at moderate incomes the solo 401(k) can allow more than double what a SEP-IRA permits. If you have a SEP-IRA and haven't revisited your plan structure since you opened it, there's a good chance you're leaving meaningful tax-sheltered contribution room on the table every year.
On This Page
- Key Takeaways
- How SEP-IRA contributions actually work (and the ceiling most people don't see)
- How the solo 401(k) unlocks higher contributions at the same income
- Comparison table: Solo 401(k) vs SEP-IRA side-by-side
- The Roth option and loan provision only solo 401(k)s offer
- Why the "simpler is better" instinct leads to lower contributions
- Maryland business owners: a local angle worth knowing
- Frequently Asked Questions
- Schedule a retirement plan review
- Disclosures
Key Takeaways
- Both plans share the same 2026 total limit of $72,000, but the solo 401(k) can reach it at a far lower income level.
- A solo 401(k) at $100,000 in net self-employment income allows roughly $43,087 — compared to about $18,587 under a SEP-IRA.
- The solo 401(k) adds a Roth deferral option, a catch-up provision after age 50, and a loan mechanism a SEP-IRA does not offer; under the SECURE 2.0 Act, some SEP-IRAs can offer a Roth option too, but availability and implementation are limited by the plan/provider.
- A SEP-IRA makes sense if you have common-law employees or strongly prefer minimal administrative setup.
- Switching from a SEP-IRA to a solo 401(k) does not require moving existing balances — you can open the new plan for the current year.
About the Author: Jeff Judge, CFP®, AEP®, ChFC®, CLU® is Managing Partner of Chesapeake Financial Planners in Forest Hill, Maryland. He has helped self-employed business owners across Harford County and the Baltimore metro area structure and fund retirement plans since earning his CFP® in 2013. Jeff works directly with independent consultants, physicians, attorneys, and tradespeople on business retirement strategy as part of their broader financial plan, by using Chesapeake Financial Planners' signature process, the R.U.D.D.E.R. method™.
How SEP-IRA contributions actually work (and the ceiling most people don't see)
The SEP-IRA's appeal is real. Setup takes roughly 20 minutes at most financial institutions. There's no separate plan document. Contributions can be made up until the tax filing deadline, including extensions, which suits a business owner whose net income isn't finalized until after the year ends. Below a $250,000 plan balance, there's no annual filing requirement.
For a business owner managing too many moving pieces, a SEP-IRA represents a retirement account that functions without much ongoing attention. The problem is that "easy" and "optimal" are not the same thing.
A SEP-IRA operates on a single lever: the employer contribution. You contribute a percentage of compensation — up to 25% for a W-2 employee, or approximately 20% of net self-employment income after the self-employment tax deduction. That's the entire mechanism. There is no salary deferral component and no catch-up for owners age 50 and older. Under the SECURE 2.0 Act, some SEP-IRAs can offer a Roth option, but availability and implementation are limited by the plan/provider.
The SEP-IRA contribution limits for 2026 is 25% of compensation (roughly 20% of net self-employment income), up to a maximum of $72,000. At $100,000 in net self-employment income, that calculates to approximately $18,587. That number is the ceiling. There is nothing else to add.
"I've seen clients contribute between $15,000 and $20,000 per year to a SEP-IRA for years when a solo 401(k) would have allowed them to shelter $40,000 or more at the same income level, with no meaningful difference in administrative complexity once the plan is established."
How the solo 401(k) unlocks higher contributions at the same income
A solo 401(k) uses two levers where the SEP-IRA uses one.
The first is the employee salary deferral. For 2026, that's up to $24,500 if you're under age 50, or $32,500 if you're 50 to 59 or 64 and older (adding the $8,000 catch-up). Owners aged 60 to 63 have access to an enhanced catch-up of $11,250 under SECURE 2.0. This deferral is available regardless of your compensation level, as long as your net self-employment income covers the contribution amount.
The second lever is the employer profit-sharing contribution, which functions similarly to a SEP-IRA: approximately 20% of net self-employment income, up to the annual additions limit of $72,000 for 2026. The two contributions combine and together can reach $72,000, or $80,000 for those age 50 to 59 or 64+ with the catch-up.
At $100,000 in net self-employment income: the employer profit-sharing component is the same $18,587 as the SEP-IRA. Add the $24,500 employee deferral and the solo 401(k) total reaches approximately $43,087. Same income. Same tax situation. More than twice the retirement contribution.
At $150,000 in net self-employment income, the gap narrows but stays meaningful. A SEP-IRA allows roughly $27,881. A solo 401(k) allows $27,881 plus $24,500, or approximately $52,381. Above roughly $300,000, both plans approach the same ceiling and the SEP-IRA becomes more competitive from a contribution standpoint alone.
Comparison table: Solo 401(k) vs SEP-IRA side-by-side
| Feature | Solo 401(k) | SEP-IRA |
|---|---|---|
| 2026 Total Limit | $72,000 ($80,000 age 50+) | $72,000 (no catch-up) |
| Employer contribution | Up to ~20% of net SE income | Up to ~20% of net SE income |
| Employee salary deferral | Yes — $24,500 ($32,500 age 50+) | None |
| Roth option | Yes (salary deferral portion) | Yes, but many plans don’t have it yet |
| Catch-up age 50+ | $8,000 ($11,250 age 60-63) | None |
| Loan provision | Yes (up to $50,000) | No |
| Employees allowed | Owner + spouse only | Yes (must contribute same % for all) |
| Setup complexity | Moderate (plan document required) | Minimal |
| Annual filing | Form 5500-EZ above $250,000 | None below $250,000 |
| Contribution deadline | Employee deferral by Dec 31; employer by tax filing deadline | Tax filing deadline including extensions |
The Roth option and loan provision only solo 401(k)s offer
A solo 401(k) can include a Roth designation for employee salary deferrals. Contributions go in after tax and the account grows without ongoing federal tax drag, with qualified distributions in retirement that don't count toward income for purposes like Social Security taxation or IRMAA Medicare premium calculations.
Under the SECURE 2.0 Act, some SEP-IRAs can offer a Roth option, but availability and implementation are limited by the plan/provider. For self-employed owners who exceed the Roth IRA income limits and phase-out rules for direct contributions — the phase-out begins at $153,000 for single filers in 2026 — the Roth 401(k) deferral inside a solo 401(k) is one of the few mechanisms for building a meaningful Roth balance annually.
There's also a How Do High Earners Open a Backdoor Roth IRA in 2026? interaction worth noting. For owners who have traditional IRA or SEP-IRA balances and want to execute a backdoor Roth conversion, a solo 401(k) that accepts incoming rollovers can absorb those IRA balances and eliminate the pro-rata tax problem. A SEP-IRA is itself a type of IRA, so it doesn't solve this issue — it compounds it.
The loan provision in a solo 401(k) allows borrowing up to $50,000 or 50% of the vested balance, whichever is less. This is not a strategy to lean on, but it exists as an option. A SEP-IRA offers no loan mechanism whatsoever.
Why the "simpler is better" instinct leads to lower contributions
The recommendation to open a SEP-IRA typically comes from an accountant, a payroll company, or a bank rep, someone focused on getting a retirement account in place with minimal friction. That's a reasonable goal. The SEP-IRA delivered.
What it didn't deliver was an ongoing comparison. Nobody circled back five years later to ask whether the structure still made sense given how the business had grown and what the owner's income actually looked like.
A solo 401(k) does require adopting a plan document. Both Fidelity and Charles Schwab offer prototype solo 401(k) plans that can be established through a standard application process at no cost. Once the plan is in place, annual administration is minimal until assets exceed $250,000, at which point a Form 5500-EZ is required.
The plan must be established by December 31 of the tax year for which you want to make the employee salary deferral. Employer profit-sharing contributions can still be made up until the tax filing deadline, including extensions — matching the SEP-IRA's flexibility on that front.
The "simpler is better" logic holds when both options are genuinely equivalent. When one option allows twice the contribution at the same income level, simplicity is a real cost.
Maryland business owners: a local angle worth knowing
Many Harford County and Bel Air business owners are still operating with SEP-IRAs set up years ago — often during the early years of a practice or consulting business — without revisiting whether the structure still serves them.
Maryland has a pass-through entity (PTE) tax election that interacts meaningfully with retirement plan deductions. When a Maryland Maryland business owner tax planning strategies evaluates how much to contribute to a retirement plan, the PTE election can affect the optimal contribution strategy and the timing of deductions. A solo 401(k) that allows larger contributions may amplify the federal deduction while the PTE election handles the state-level piece — but the two levers need to be coordinated.
Forest Hill, Bel Air, and the broader Harford County business owner community tends to skew toward independent practice owners and tradespeople with moderate to upper-moderate self-employment income — exactly the range where the contribution gap between a SEP-IRA and a solo 401(k) is largest.
This is the kind of review that belongs inside the R.U.D.D.E.R. Method™, Chesapeake Financial Planners' six-step planning process: Review and Recognize, Uncover and Understand, Design and Develop, Discuss and Decide, Execute and Empower, and Reassess and Refine. Plan structure decisions live in the Design and Develop phase, but they require Review and Recognize to surface in the first place. A SEP-IRA that was appropriate at $80,000 in net income may not be the right structure at $140,000. The question needs to come up regularly, not just once. Jeff Judge notes: "A SEP-IRA that made perfect sense at $80,000 in self-employment income can quietly cost a Harford County owner thousands in foregone deferrals once net income climbs past $120,000 or $130,000, and most owners never get the prompt to revisit it."
Frequently Asked Questions
Can I contribute to both a solo 401(k) and a SEP-IRA in the same year?
No. If both plans are for the same business, the IRS treats them as the same employer plan and the limits are combined. You choose one structure or the other for a given tax year. If you have a W-2 job with its own 401(k) alongside a self-employed business, the plans are for separate employers and can coexist — though the employee deferral limit is shared across all 401(k) accounts.
What happens to my SEP-IRA balance if I switch to a solo 401(k)?
Nothing, unless you choose to act. The existing SEP-IRA balance stays where it is. You simply open a solo 401(k) for the current or future tax year and begin making contributions to the new plan. If your solo 401(k) accepts incoming rollovers and you want to consolidate, you can roll the SEP-IRA balance into the 401(k) later — but that step is optional and separate from simply establishing the new plan.
I'm 58 years old. How much more can I contribute to a solo 401(k) versus a SEP-IRA at $120,000 in net income?
At $120,000 in net self-employment income, a SEP-IRA allows approximately $22,305. A solo 401(k) allows that same $22,305 employer contribution plus the $24,500 employee deferral plus the $8,000 age-50+ catch-up, for a total of approximately $54,805. The gap is roughly $32,500 in a single year — sheltered from current federal and Maryland income tax.
Does a solo 401(k) have to be established before December 31?
Yes, for the employee salary deferral. If you want to make an employee deferral contribution for a given tax year, the plan must be established by December 31 of that year. The employer profit-sharing contribution can be made up until your tax filing deadline, including extensions. A SEP-IRA can be established and funded up until the filing deadline — which gives it a flexibility edge for owners who didn't finalize their plan until after year-end.
I have one part-time employee. Does that disqualify me from a solo 401(k)?
It depends on how the employee is classified and whether they meet the eligibility requirements. A solo 401(k) is available to business owners with no employees other than a spouse. If you have a common-law employee who has worked more than 1,000 hours in a plan year, the solo 401(k) is no longer available. Part-time employees below that threshold generally don't disqualify the plan, but this is a fact-specific question that warrants direct review — plan eligibility rules have specific definitions for "employee" and "hours of service."
What is the deadline to establish a solo 401(k) for 2026?
The plan must be established by December 31, 2026 to make employee salary deferrals for that tax year. Employer profit-sharing contributions for 2026 can be made up until the tax filing deadline for 2026, including any extensions. This means a self-employed person who files on extension has until October 2027 to make the employer portion of the 2026 contribution — even if the plan was opened on December 30, 2026.
Schedule a retirement plan review
If you're self-employed and haven't revisited your retirement plan structure since you first set it up, that review is worth scheduling. The right structure isn't whichever plan was simplest to open — it's whichever one lets you shelter the most, in the right accounts, given where your business is today.
Jeff Judge and the Chesapeake Financial Planners team work directly with self-employed owners across Harford County, Bel Air, Forest Hill, and the Baltimore metro area on exactly this kind of review. Schedule a complimentary consultation at chesapeakefp.com to walk through your current plan structure and what a change might mean for your 2026 contributions.
This post is adapted from 'Solo 401(k) Almost Always Better Than SEP-IRA' originally published on Chesapeake Financial Planners' LinkedIn.
Disclosures
The information provided is for educational purposes only and should not be construed as investment advice. Investment strategies should be tailored to individual circumstances, risk tolerance, and goals. Past performance doesn't guarantee future results. Consult with qualified financial professionals regarding your specific situation.
Contributions to a traditional IRA may be tax deductible in the contribution year, with current income tax due at withdrawal. Withdrawals prior to age 59 ½ may result in a 10% IRS penalty tax in addition to current income tax.
Advisors associated with Chesapeake Financial Planners may be either (1) LPL Financial Registered Representatives offering securities through LPL Financial, Member FINRA and SIPC, and investment advisor representatives offering investment advice through Great Valley Advisor Group; or (2) solely investment advisor representatives offering investment advice through Great Valley Advisor Group and not affiliated with LPL Financial. Great Valley Advisor Group, and Chesapeake Financial Planners are separate entities from LPL Financial.
