Solo 401(k) vs SEP IRA: Which Is Better for Freelancers?

Why This Comparison Matters

If you freelance, contract, or run a one-person business, the difference between a Solo 401(k) and a SEP IRA can mean tens of thousands of dollars in extra retirement savings each year — or thousands of dollars in unnecessary tax. The plans look similar on paper because they share the same $70,000 overall cap in 2026, but the math underneath is very different. The Solo 401(k) lets a freelancer at $80,000 of income shelter nearly $40,000. A SEP IRA at the same income shelters only about $15,400.

The right choice depends on three things: how much you make, when you decide, and whether you have employees. This guide walks through all three.

2026 Contribution Limits Side-by-Side

The two plans share an identical $70,000 ceiling, but only the Solo 401(k) gives you a head start through the $24,500 employee deferral. That single feature is the reason it dominates for most freelancers.

Which Plan Wins at Each Income Level?

The 25% employer contribution percentage is the same in both plans, so the only difference is whether you also get the $24,500 employee deferral. The Solo 401(k) wins until your income is high enough that 25% alone hits the $70,000 cap. Here is the breakdown for a sole proprietor with no W-2 income:

(These figures use the standard formula that net SE income is reduced by half of self-employment tax before applying the 25% employer percentage; the actual effective rate works out to about 20% of net SE income.)

The takeaway: the Solo 401(k) gives you a fixed $24,500 head start at every income level until you hit the cap. SEP IRAs only catch up around $345,000 of net SE income. If you make less than that and you do not have employees, the Solo 401(k) is mathematically the better plan.

A Worked Example: Freelancer Earning $80,000

Say you are a freelance designer with $80,000 in net self-employment income, no W-2 job, and no employees. Here is how each plan stacks up.

Solo 401(k) Maximum

• Employee elective deferral: $24,500
• Employer contribution (about 20% of net SE income after the half-SE-tax adjustment): ~$15,400
• Total: ~$39,900

SEP IRA Maximum

• Employer contribution only: ~$15,400
• Total: ~$15,400

That is a $24,500 gap — identical to the employee deferral the SEP IRA simply does not allow. At a 24% marginal federal bracket, that extra contribution is worth roughly $5,880 in immediate federal tax savings, plus state tax savings on top.

You can sanity-check the employer-side number with our self-employment tax estimator, which computes net SE income after the half-SE-tax deduction.

Setup Mechanics

Solo 401(k)

• Setup deadline: The plan must be established by December 31 of the tax year for which you want to make employee deferrals. Miss that date and you cannot defer for the year.
• Where to open: Vanguard, Fidelity, Schwab, and E*TRADE all offer free Solo 401(k) plans with no setup or annual fee. Specialty providers offer self-directed plans with more flexibility but typically charge fees.
• Required: An EIN from the IRS (free, takes minutes online).
• Annual paperwork: Once your plan’s assets exceed $250,000, you must file Form 5500-EZ each year. Below that threshold, no annual filing is required.
• Funding: Employee deferrals must generally be designated by year end and deposited shortly after. Employer contributions can be made up to your tax filing deadline (including extensions).

SEP IRA

• Setup deadline: You can open and fund a SEP up to your tax filing deadline, including extensions. That can be as late as October 15 of the following year.
• Where to open: Most major brokerages (Vanguard, Fidelity, Schwab) offer free SEP IRAs.
• Required: IRS Form 5305-SEP, a one-page document you fill out and keep on file. You do not file it with the IRS.
• Annual paperwork: None.
• Funding: Employer contributions only, deposited by the tax filing deadline.

When the SEP IRA Still Wins

Despite the math, plenty of freelancers are better off with a SEP IRA. Here is when:

• You missed the December 31 deadline. If it’s February and you’re filing taxes for last year, the Solo 401(k) door is closed for the prior year. The SEP IRA is still wide open until April 15 (or October 15 with an extension).
• You want maximum simplicity. No plan documents to maintain, no Form 5500-EZ to track, no employee/employer split to calculate. The SEP is one form, one account, one annual contribution.
• You expect inconsistent income. The SEP’s funding flexibility through the tax extension deadline means you can wait to see your actual numbers before deciding how much to contribute.
• Your income is well above $345,000. Above that threshold both plans hit the same $70,000 cap, so you might as well use the simpler one.

What Changes If You Have Employees

This is the single biggest disqualifier for a Solo 401(k). The plan is restricted to business owners and their spouses. Hiring even one full-time W-2 employee (typically defined as someone working 1,000+ hours per year and not your spouse) ends your eligibility. You would need to convert to a regular 401(k), which carries higher administrative costs, ERISA compliance, and nondiscrimination testing.

A SEP IRA can include employees, but with a catch: you must contribute the same percentage of compensation for every eligible employeethat you contribute for yourself. If you contribute 20% of your net SE income, you must also contribute 20% of each eligible employee’s W-2 wages. For most small employers, this gets expensive fast.

If you are a true solo operator (or solo + spouse), the Solo 401(k) is the obvious pick. The moment you hire your first non-spouse employee, the calculus flips entirely.

Roth and Mega-Backdoor Roth

One of the underrated advantages of the Solo 401(k) is the Roth option. You can elect to make all or part of your $24,500 employee deferral as Roth, paying tax now in exchange for tax-free growth and withdrawals in retirement. SEP IRAs, while technically allowed to accept Roth contributions under SECURE 2.0, are still rarely supported by custodians as of 2026.

Some Solo 401(k) custodians also allow after-tax (non-Roth) employee contributions with in-plan Roth conversions — the so-called mega-backdoor Roth. Done correctly, this lets a high-earning freelancer push tens of thousands of dollars into Roth space each year, far above the standard $24,500 deferral. Most "free" providers (Vanguard, Fidelity, Schwab) do not support this; you typically need a custom or self-directed plan to access it.

If Roth matters to you — which it usually does for younger freelancers or anyone expecting higher tax brackets in retirement — the Solo 401(k) wins decisively.

Common Mistakes to Avoid

Missing the December 31 Solo 401(k) Deadline

This is the most expensive mistake freelancers make. You cannot retroactively open a Solo 401(k) for last year if the plan didn’t exist by December 31. If you’re even thinking about a Solo 401(k) for the current year, open it before year end. The plan can sit empty — what matters is that it exists.

Exceeding the 25% Employer Limit

The 25% employer contribution is calculated on net SE income afterthe deduction for half of self-employment tax. The effective rate for sole proprietors is closer to 20% of net SE income, not 25% of gross. Get this wrong and you’ll have an excess contribution that triggers a 10% excise tax and requires a corrective distribution.

Forgetting Form 5500-EZ

Once your Solo 401(k) balance crosses $250,000, you owe an annual Form 5500-EZ filing. The penalty for failing to file can be steep — up to $250 per day, capped at $150,000. Set a calendar reminder.

Accidentally Disqualifying Yourself

Hiring a non-spouse W-2 employee voids your Solo 401(k) eligibility. If you’re scaling and considering hires, plan ahead: convert to a regular 401(k) or switch to a SEP IRA before the hire, not after.

Choosing Based on Catch-Up Marketing

Catch-up contributions only apply if you’re 50 or older. If you’re 35 and choosing a plan, the $8,000 catch-up is irrelevant for the next 15 years. Focus on the deferral and Roth advantages instead.

Decision Framework

Use this quick filter to choose:

• Solo + no employees + decided before Dec 31? Solo 401(k).
• Solo + missed Dec 31? SEP IRA for this year, then open a Solo 401(k) before December 31 for next year.
• You have or plan to hire W-2 employees? SEP IRA (or upgrade to a regular 401(k) / SIMPLE IRA).
• Net SE income above $345,000 and no Roth need? SEP IRA — same cap, less paperwork.
• You want Roth or a participant loan? Solo 401(k).

Related Reading

• How to Calculate Self-Employment Tax in 2026 — the foundation for figuring net SE income.
• Quarterly Estimated Tax Payments Guide — pair retirement contributions with quarterly planning.
• Freelance Rate Calculator Guide — price your work to actually leave room for retirement contributions.
• 401(k) Calculator — model long-term growth on your Solo 401(k) contributions.

Frequently Asked Questions

Is a Solo 401(k) better than a SEP IRA?

For most freelancers earning under about $280,000 in net self-employment income, the Solo 401(k) is better. It allows a $24,500 employee deferral on top of the 25% employer contribution, while the SEP IRA only allows the 25% employer piece. Both share the same $70,000 overall 2026 cap, but the Solo 401(k) lets you reach it at a much lower income. The Solo 401(k) also offers catch-up contributions, a Roth option, and participant loans.

What is the contribution limit for a Solo 401(k) in 2026?

In 2026, the Solo 401(k) limit is $70,000 total. That breaks down into a $24,500 employee elective deferral plus an employer contribution of up to 25% of net self-employment income. People age 50 and over can add an $8,000 catch-up contribution, and those age 60 to 63 qualify for an enhanced $11,250 super catch-up.

Can I open a Solo 401(k) after the year ends?

No. To make any employee deferrals for a given tax year, the Solo 401(k) plan must be established by December 31 of that year. The SECURE Act allows the employer profit-sharing portion to be funded up to your tax filing deadline, but the plan itself must exist by year end. SEP IRAs are more flexible: you can open and fund a SEP up to the tax filing deadline, including extensions.

Does a SEP IRA allow Roth contributions?

SEP IRAs traditionally do not allow Roth contributions. While SECURE 2.0 created the option for Roth SEP contributions, custodian adoption has been slow and most providers still only support traditional pre-tax SEP contributions. Solo 401(k)s, by contrast, widely support Roth on the employee deferral and increasingly on the employer side, making them the better choice if Roth is a priority.

Can I have a Solo 401(k) if I have employees?

No. A Solo 401(k) is restricted to business owners and their spouses. Hiring even one full-time W-2 employee (other than your spouse) disqualifies you from the Solo 401(k), and you would need to convert to a regular 401(k) plan. A SEP IRA can include employees, but you must contribute the same percentage of compensation for every eligible employee that you contribute for yourself.