Solo 401(k) vs SEP-IRA for Freelancers (2026 Limits)

A solo 401(k) lets a freelancer contribute more than a SEP-IRA at the same income — because it adds a $24,500 employee deferral on top of the same employer contribution a SEP allows. On $100,000 of net profit in 2026: a SEP-IRA caps at about $18,587, a solo 401(k) at about $43,087. Both share the same $72,000 overall limit, so the advantage disappears only once profit is high enough to hit it.

Solo 401(k) vs SEP-IRA: the structural difference

Both plans let a self-employed person make an employer contribution of up to 25% of compensation — which works out to 20% of net earnings once you account for the plan compensation rules. That part is identical.

The difference is that a solo 401(k) treats you as both employer and employee, so you also get the employee deferral: $24,500 in 2026. A SEP-IRA has no employee side at all. That single feature is the entire gap between the two plans at most income levels.

What each plan allows at your profit level

“Plan compensation” is your net profit minus half your self-employment tax — the figure both plans actually apply their percentage to. If that deduction is unfamiliar, the self-employment tax guide walks through where it comes from.

The 2026 limits that govern both plans

Two thresholds follow from these. A solo 401(k) reaches the $72,000 ceiling at $237,500 of plan compensation ($24,500 + 20%). A SEP-IRA does not reach it until $360,000. Between those two points the solo 401(k)’s advantage shrinks; above $360,000 the two plans are identical.

Where the SEP-IRA still wins

• Setup and paperwork. A SEP is a one-form account you can open at any brokerage in an afternoon. A solo 401(k) requires a plan document, and once assets pass $250,000 an annual Form 5500-EZ filing.
• Deadline flexibility. A SEP can be established and funded up to your tax filing deadline including extensions — so it can be opened after year-end to cut a tax bill you have already incurred. The solo 401(k) employee deferral is bound to much tighter election timing.
• Employees. A solo 401(k) is only for an owner (and spouse) with no other full-time employees. Hire one and the plan has to change. A SEP can cover employees — though it must then fund them at the same percentage as the owner, which gets expensive quickly.

How this lands on your quarterly tax payments

Both plans reduce your taxable income in the year you contribute, which reduces the estimated payments you owe across the year — not just the April number. A freelancer at $100,000 profit who contributes $43,087 to a solo 401(k) has removed a substantial slice of income before the rate schedule ever touches it.

What neither plan reduces is self-employment tax. That is levied on net earnings before retirement contributions, so your Social Security and Medicare bill is the same either way. Only income tax moves. Work the change through your quarterly tax filing rather than waiting until filing season to find out what it did.

Key takeaways

• A solo 401(k) beats a SEP-IRA by exactly the $24,500 employee deferral at most income levels.
• On $100,000 of net profit in 2026: about $18,587 into a SEP versus about $43,087 into a solo 401(k).
• Both share a $72,000 overall limit; the solo 401(k) reaches it at $237,500 of plan compensation, the SEP not until $360,000.
• The SEP wins on simplicity and on deadlines — it can be opened and funded after year-end, including extensions.
• Neither plan reduces self-employment tax; both reduce income tax, so both should change your quarterly estimates.