What Are the Solo 401(k) Contribution Limits for 2026?

A solo 401(k) has one trick that makes it the biggest retirement account most self-employed people can access: you contribute twice, once as the employee and once as the employer.

That stacking is why a one-person business can shelter far more here than in an IRA or even a SEP IRA. For 2026, the combined limit reaches $72,000 and higher with catch-ups.

This guide breaks down the 2026 employee and employer limits, the combined cap, catch-up contributions, the self-employed math that trips people up, the new Roth catch-up rule, and how it all compares to a SEP IRA.

Key takeaways

• For 2026, the solo 401(k) employee deferral limit is $24,500, up from $23,500 in 2025.
• The combined employee-plus-employer limit is $72,000 (before catch-ups).
• The age 50–59 catch-up is $8,000, raising the total to $80,000.
• The age 60–63 super catch-up is $11,250, raising the total to $83,250.
• Self-employed owners calculate the employer contribution on net earnings, which works out to roughly 20%, not a flat 25%.

How a solo 401(k) works: two hats

The reason a solo 401(k) allows such large contributions is that you play two roles in your own business. You're the employee, so you can make a salary deferral, and you're the employer, so your business can make a profit-sharing contribution on top.

Most retirement accounts only let you contribute in one capacity. A traditional IRA caps you at the individual limit; a SEP IRA is employer-only. The solo 401(k) combines both, which is what pushes the ceiling so high for an owner-only business.

The catch is that the two contributions don't stack without limit. Both roll up into a single annual cap, so understanding how the pieces fit is the whole game.

The 2026 contribution limits

Here are the numbers for 2026, set by IRS Notice 2025-67. As the employee, you can defer up to $24,500 of your compensation, up from $23,500 in 2025. As the employer, your business can contribute up to 25% of compensation on top of that.

The combined total of both contributions is capped at $72,000 for 2026, not counting catch-ups. This is the annual additions limit under Section 415(c), and it's the number to anchor on. You can contribute up to that combined cap, or 100% of your compensation, whichever is less.

The IRS one-participant 401(k) page is the authoritative source, and these limits adjust annually, so confirm the current figures each year.

Catch-up contributions

If you're older, you can contribute more. Catch-up contributions sit on top of the standard limits and don't count against the $72,000 combined cap.

For 2026, participants age 50 and older can add a catch-up of $8,000, lifting the total ceiling to $80,000. There's also a super catch-up under SECURE 2.0 for participants ages 60 to 63, worth $11,250 for 2026, which raises the ceiling to $83,250.

The super catch-up replaces the $8,000 figure for those ages rather than stacking on top of it.

Catch-ups are among the most valuable features of a solo 401(k) versus a SEP IRA, which allows no catch-up contributions at all. For anyone over 50 trying to maximise retirement savings late, that difference matters.

The self-employed math

This is where people over-contribute by accident. The 25% employer contribution sounds simple, but for a self-employed owner it isn't calculated on gross income.

For a sole proprietor, the employer contribution is based on net earnings from your Schedule C, reduced by half of your self-employment tax and by the contribution itself.

Because of that circular adjustment, the effective employer rate works out to roughly 20% of net earnings, not 25%. Skipping the half-SE-tax step is one of the most common ways owners over-contribute.

For an S-corporation owner, the math is cleaner because it runs off W-2 wages. Employee deferrals and the 25% employer contribution are both based on your W-2 compensation.

That's one reason business structure matters here, and why the S-corp versus sole-prop choice affects how much you can contribute. In both cases, run the numbers rather than assuming a flat percentage.

The 2026 Roth catch-up rule

A new rule takes effect in 2026 that solo 401(k) owners should know about. Under SECURE 2.0, if your prior-year FICA wages exceeded $150,000, any catch-up contributions you make must be Roth, meaning after-tax, rather than pre-tax.

For employees in a standard workplace plan, this is straightforward. For self-employed solo 401(k) owners, the application is more nuanced and depends on your structure and how wages are defined, but the practical takeaway is that your plan must support Roth contributions for higher earners to make catch-ups at all.

If your solo 401(k) is a basic plan that doesn't offer Roth, this rule could block your catch-up entirely. It's worth checking with your provider, and our guide to traditional versus Roth accounts covers the tax trade-off.

Solo 401(k) vs SEP IRA

The most common question is which lets you save more. At higher incomes, they can reach the same $72,000 cap. The difference shows up at lower and moderate incomes.

Because a solo 401(k) includes a flat $24,500 employee deferral regardless of the 25% calculation, a moderate-income owner can often contribute more to a solo 401(k) than a SEP IRA at the same income.

A SEP IRA relies entirely on the percentage-of-income calculation, so it takes more income to reach the same total. The solo 401(k) also allows catch-ups and Roth options, which a SEP IRA doesn't.

The trade-off is complexity. A SEP IRA is simpler to set up and administer, while a solo 401(k) has more rules and, at higher balances, a filing requirement. Our guide to the SEP IRA covers that side in full.

Deadlines and setup

Timing differs for the two contribution types. You generally must establish the solo 401(k) plan by December 31 of the tax year to contribute for that year, so a plan for 2026 needs to exist by the end of 2026.

Employee deferrals typically must be elected by year-end, while the employer profit-sharing contribution can be made up to your tax filing deadline, including extensions. That gives you room to finalize your numbers and fund the employer side after year-end.

Because your contribution capacity depends on your net earnings or W-2 wages, accurate books are what let you calculate it correctly. Finlens keeps your books current so your net profit is right when you compute your maximum contribution, and so you don't discover an over-contribution after the fact.

Conclusion

The solo 401(k) is the highest-ceiling retirement plan most self-employed people can use. For 2026 the numbers are clear: $24,500 as the employee, up to 25% of compensation as the employer, a $72,000 combined cap, and $80,000 or $83,250 with catch-ups.

The trap is the employer math. For sole proprietors, the 25% is really closer to 20% of net earnings once self-employment tax is accounted for, so calculate carefully rather than assuming the headline percentage. And if you're a high earner over 50, check that your plan supports Roth so the new catch-up rule doesn't block you.

Run your contribution off accurate net income, mind the combined cap and the deadlines, and the solo 401(k) is one of the most powerful tools a self-employed saver has.

Frequently asked questions

What is the solo 401(k) contribution limit for 2026?

For 2026, you can defer up to $24,500 as the employee, plus an employer contribution of up to 25% of compensation, for a combined limit of $72,000 before catch-ups. With the age 50–59 catch-up, the total reaches $80,000, and with the age 60–63 super catch-up, $83,250.

How much can the employer side of a solo 401(k) contribute?

The employer can contribute up to 25% of compensation, subject to the $72,000 combined cap. For an S-corporation owner, that 25% is based on W-2 wages. For a sole proprietor, it's based on net earnings after adjustments, which makes the effective rate closer to 20% rather than a flat 25%.

What are the solo 401(k) catch-up contributions for 2026?

Participants age 50 and older can add an $8,000 catch-up, raising the total ceiling to $80,000. Those ages 60 to 63 get a larger super catch-up of $11,250 under SECURE 2.0, raising the ceiling to $83,250. The super catch-up replaces the $8,000 for those ages rather than adding to it.

Why is my solo 401(k) employer contribution not 25%?

For a self-employed sole proprietor, the 25% is calculated on net earnings after deducting half of your self-employment tax and the contribution itself. That circular adjustment reduces the effective rate to roughly 20% of net earnings. S-corporation owners calculate 25% on W-2 wages instead, which is more straightforward.

Solo 401(k) vs SEP IRA: which lets me contribute more?

At higher incomes both can reach $72,000. At lower and moderate incomes, a solo 401(k) usually allows more, because its flat $24,500 employee deferral is added regardless of the percentage calculation. A SEP IRA relies entirely on the percentage, and it doesn't allow catch-ups or Roth contributions.

What is the 2026 Roth catch-up rule?

Starting in 2026, under SECURE 2.0, if your prior-year FICA wages exceeded $150,000, your catch-up contributions must be made as Roth (after-tax) rather than pre-tax. If your plan doesn't offer Roth, affected high earners can't make catch-up contributions at all, so plan design matters.

When do I have to set up a solo 401(k) to contribute for 2026?

You generally must establish the plan by December 31, 2026, to contribute for the 2026 tax year. Employee deferrals are usually elected by year-end, while the employer profit-sharing contribution can be made up to your tax filing deadline, including extensions.

Can I contribute to a solo 401(k) and a regular IRA?

Yes. A solo 401(k) doesn't count against your personal IRA contribution limit, so you can contribute to both in the same year. Your IRA deduction may be limited by income if you're covered by the solo 401(k), so check the traditional IRA deduction rules for your situation.