One of the perks of working for yourself is that nobody else decides how you save for retirement. One of the downsides is exactly the same thing. There is no employer setting up a 401k, no automatic enrollment, and no match showing up in your account every pay period. The entire decision falls on you, and for many self-employed people that decision comes down to two options: the SEP-IRA and the Solo 401k.
Both let you shelter a meaningful amount of income from taxes every year, and both are far more powerful than a regular IRA. But they work differently, and at most income levels one of them lets you put away significantly more money than the other for the exact same income. This guide walks through how each plan works in 2026, where the real differences are, and how to figure out which one fits your situation.
Why This Decision Is Worth Getting Right
Every dollar you contribute to either plan reduces your taxable income for the year, which lowers both your federal income tax and the base used to calculate your self-employment tax. That makes retirement contributions one of the most effective tax reduction tools available to a self-employed person, on top of building long-term savings.
The two plans are not interchangeable in how much they let you contribute. At lower and moderate income levels, the gap between them is large enough to mean tens of thousands of dollars in additional tax-deferred savings over a few years, simply by choosing the right structure.
What a SEP-IRA Actually Is
SEP stands for Simplified Employee Pension. A SEP-IRA is an individual retirement account that you, as a self-employed person, fund in the role of employer. The defining feature is right there in the name: it is simple. There is no annual IRS filing requirement, no plan document to maintain, and almost no administrative burden beyond opening the account at a brokerage and making a contribution.
For 2026, you can contribute up to 25 percent of your compensation, capped at $72,000. Because contributions come entirely from the employer side, there is no employee deferral component at all. If you are self-employed and not running payroll, the practical contribution limit works out to roughly 20 percent of your net self-employment income after the self-employment tax adjustment, rather than a clean 25 percent.
This structure means reaching the full $72,000 limit requires a substantial income. You would need net self-employment earnings somewhere in the range of $280,000 to $288,000 to max out a SEP-IRA in 2026. Below that level, your contribution scales down proportionally with your income.
One detail that catches people off guard: if you ever hire employees, you are generally required to contribute the same percentage of compensation for them that you contribute for yourself. That can make a SEP-IRA expensive once a business grows beyond a solo operation.
What a Solo 401k Actually Is
A Solo 401k, also called an Individual 401k or One-Participant 401k, is built for a business owner with no employees other than a spouse. The key structural difference from a SEP-IRA is that you contribute in two separate roles, as the employee and as the employer, and that second contribution bucket is what changes the math significantly at lower income levels.
As the employee, you can defer up to $24,500 in 2026, regardless of your income, as long as you earned at least that much. If you are between 50 and 59, or 64 and older, you can add a standard catch-up contribution of $8,000, bringing your employee deferral to $32,500. If you are between 60 and 63, SECURE 2.0 allows an enhanced catch-up of $11,250 instead, for a total employee deferral of $35,750.
As the employer, you can contribute an additional 25 percent of your compensation, calculated the same way as a SEP-IRA.
The combined total across both contribution buckets cannot exceed $72,000 in 2026, or $80,000 with the standard catch-up, or $83,250 with the enhanced catch-up for ages 60 through 63.
Side by Side: Where the Real Differences Are
| Feature | SEP-IRA | Solo 401k |
|---|---|---|
| 2026 contribution limit | Up to $72,000 | Up to $72,000, more with catch-up |
| Employee deferral | Not available | Up to $24,500 regardless of income |
| Employer contribution | Up to 25% of compensation | Up to 25% of compensation |
| Catch-up at 50+ | Not available | $8,000, or $11,250 for ages 60–63 |
| Roth option | Technically allowed since SECURE 2.0, but few providers support it | Widely available |
| Loan against the balance | Not available | Up to $50,000 or 50% of vested balance |
| Works if you have employees | Yes, but you must contribute the same percentage for them | No, owner and spouse only |
| Annual IRS filing | None required | Form 5500-EZ once assets exceed $250,000 |
| Setup deadline | Tax filing deadline, including extensions | December 31 of the plan year |
Where the Contribution Gap Actually Shows Up
The advantage of the Solo 401k is concentrated almost entirely in the employee deferral, and it matters most at lower and moderate income levels where a SEP-IRA’s 25 percent cap simply does not generate much room on its own.
Take a 45-year-old freelancer with $80,000 in net self-employment income in 2026. Under a SEP-IRA, the maximum contribution comes out to roughly $14,500, based on the 20 percent effective limit after the self-employment tax adjustment. Under a Solo 401k, the same freelancer can contribute $24,500 as the employee plus roughly $14,500 as the employer, for a total of about $39,000. That gap, $24,500 in this example, is the entire employee deferral, and it shows up at almost any income level because it does not depend on how much you earned.
| Net Self-Employment Income | SEP-IRA Maximum | Solo 401k Maximum | Gap |
|---|---|---|---|
| $40,000 | ~$8,000 | ~$32,500 | ~$24,500 |
| $80,000 | ~$14,500 | ~$39,000 | ~$24,500 |
| $150,000 | ~$30,000 | ~$54,500 | ~$24,500 |
| $200,000 | ~$40,000 | ~$64,500 | ~$24,500 |
| $280,000+ | ~$70,000 to $72,000 | ~$72,000 | Roughly equal |
The gap stays close to the size of the employee deferral right up until your income gets high enough that the employer-side 25 percent contribution alone approaches the overall cap, at which point both plans converge near the same maximum.
When a SEP-IRA Still Makes Sense
Despite the contribution gap, there are real situations where a SEP-IRA is still the better fit. If you currently have employees, or expect to hire soon, the Solo 401k is not available to you at all, since it is restricted to owners and spouses with no other staff. A SEP-IRA allows employees, though the requirement to match their contribution percentage to your own makes it considerably more expensive once you are not the only person on payroll.
If administrative simplicity matters more to you than maximizing contributions, the SEP-IRA wins clearly. There is no Form 5500-EZ to worry about even at higher balances, no December 31 setup deadline, and you can decide how much to contribute as late as your tax filing deadline, including extensions. That flexibility lets you wait until you know exactly how your year turned out financially before committing to a number.
If your income is already high enough that you are contributing close to the $72,000 ceiling through the employer side alone, the Solo 401k’s extra room from the employee deferral does not add much practical benefit, since you are near the same overall limit either way.
When a Solo 401k Makes More Sense
For most self-employed people earning under roughly $200,000, the Solo 401k is the stronger choice, and the gap is largest precisely in the income range where most freelancers actually fall.
The employee deferral is the reason. It lets you contribute a meaningful amount even in a lower-income year, since it does not depend on a percentage of your earnings the way the employer contribution does. A freelancer coming off a slow year with $40,000 in net profit can still defer up to $24,500 as the employee, something a SEP-IRA simply cannot replicate at that income level.
The Roth option is a second real advantage. While SEP-IRAs technically gained the ability to accept Roth contributions under SECURE 2.0, very few custodians have actually built the infrastructure to support it, which makes the option mostly theoretical in practice. A Solo 401k’s Roth feature, by contrast, is widely available and lets you make after-tax contributions that grow and withdraw completely tax-free in retirement, which is particularly useful if you expect to be in a higher bracket later in your career.
The loan provision is unique to the Solo 401k as well. You can borrow up to $50,000 or half your vested balance, whichever is smaller, and repay it over time without triggering the taxes and penalties of an early withdrawal. Most people never need this, but it is a safety net the SEP-IRA does not offer at all.
The Deadlines Work Very Differently
This is one of the most practical differences and it catches people off guard if they are setting up a plan late in the year.
A SEP-IRA can be opened and funded as late as your tax filing deadline, including extensions. If you file for an extension, that gives you until mid-October of the following year to both establish and fund a SEP-IRA for the prior tax year. This is one of the most underused features of the SEP-IRA, since it lets you decide your contribution after you already know exactly how your year performed financially.
A Solo 401k works differently. The plan itself must be established by December 31 of the tax year you want it to count for. You cannot open a Solo 401k in January and apply it retroactively to the prior year the way you can with a SEP-IRA. Once the plan exists, employer contributions can still be made up to your filing deadline including extensions, but employee deferrals specifically must go in before December 31.
If it is already late in the year and you have not set up a Solo 401k, a SEP-IRA may be your only realistic option for that tax year, with the Solo 401k becoming available starting the following January for the next year going forward.
Can You Have Both at the Same Time?
Technically yes, but it rarely makes sense to run both simultaneously, since the IRS caps total contributions across defined contribution plans at the same overall limit. Having both does not let you double your contribution room.
The more common scenario is a transition, moving from a SEP-IRA to a Solo 401k once your income grows enough that the employee deferral becomes meaningful, or maintaining a SEP-IRA for one business that has employees while running a Solo 401k for a separate solo operation. If your situation involves either of these, a CPA who works with self-employed clients can walk through the specifics before you make a change.
The Tax Impact in Real Numbers
Both plans reduce your taxable income dollar for dollar with pre-tax contributions, which lowers your federal income tax and the income used to calculate your self-employment tax. A freelancer in the 22 percent federal bracket who contributes $20,000 to either plan saves roughly $4,400 in federal income tax in the year the contribution is made, on top of whatever growth that money generates over time inside the account.
Combined with other deductions available to self-employed people, including health insurance premiums and ordinary business expenses, aggressive retirement contributions are one of the few tools that can meaningfully bring down a freelancer’s effective tax rate compared to an employee earning a similar income. For a full picture of what else reduces your tax bill, see our freelancer tax deductions guide.
Frequently Asked Questions
Do I have to contribute the same amount every year?
No. Both plans let you vary your contribution year to year, or skip a year entirely if income is low. This flexibility fits well with the reality of variable freelance income, where some years simply do not support a large contribution.
What happens to my Solo 401k if I hire a full-time employee?
If you hire someone who is not your spouse and who works more than 1,000 hours in a year, you generally can no longer use a Solo 401k. At that point you would need to either roll the funds into an IRA or a different plan type, or convert the plan into a standard 401k that covers employees, which involves significant added administration.
Can I roll over an old 401k from a previous employer into either of these?
Yes. Both a SEP-IRA and a Solo 401k accept rollovers from traditional IRAs and prior employer 401k plans, which can be a good way to consolidate old retirement accounts into one you actively manage.
Is the Roth option worth using if it is available to me?
Roth contributions go in after tax, so you skip the immediate deduction. In exchange, all future growth and qualified withdrawals come out completely tax-free. This tends to make the most sense if you expect to be in a higher tax bracket in retirement than you are now, or if you simply want some tax diversification across your accounts. If your current income already puts you in a high bracket, the traditional pre-tax approach usually wins for now.
Final Thoughts
For most self-employed people earning under roughly $200,000, the Solo 401k provides meaningfully more contribution room for the exact same income, mainly because the employee deferral does not depend on how much you earned. The gap narrows as income climbs and largely disappears once you are contributing near the overall $72,000 ceiling through the employer side alone.
If you value simplicity, expect to bring on employees, or want the flexibility to decide your contribution after your tax year is already finished, the SEP-IRA remains a genuinely solid option with far less administrative overhead. Whichever you choose, the decision is worth running past a CPA who works with self-employed clients, since the right answer depends on your specific income, age, and plans for the business going forward.
Disclaimer: This article is for informational and educational purposes only and does not constitute financial, tax, or legal advice. Retirement plan rules, contribution limits, and tax implications vary by individual circumstances and are subject to change. Always consult a qualified financial advisor or CPA before making retirement planning decisions.