Find the most you can contribute to a one-participant 401(k). You wear two hats: as the employee you can defer up to the yearly limit, and as the employer you add a profit-sharing contribution of 20% of net earnings (sole proprietor) or 25% of W-2 salary (S corporation).
Last updated:
50+ adds a catch-up; 60–63 a larger one.
Business type
$
Schedule C line 31.
$
Box 5 Medicare wages is a good figure.
$
e.g. from a day job this year.
%
Enter your values to see the result.
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How to use the Solo 401(k) Contribution Calculator
Pick the tax year and enter your age at the end of that year.
Choose your business type. LLCs taxed as sole proprietorships use the first option.
Enter net profit or your S corp W-2 salary.
Add deferrals made to other 401(k) or 403(b) plans this year, if any.
Press Calculate solo 401(k) to see each piece and the SEP IRA comparison.
How the maximum is calculated
Employee deferral = min(yearly deferral limit − deferrals in other plans, your compensation)
Catch-up = $8,000 at 50+ or $11,250 at 60–63 (2026), if compensation allows
Employer contribution = 25% of W-2 salary (S corp) or 20% × (net profit − ½ SE tax) (sole proprietor)
Cap: deferral + employer ≤ $72,000 (2026); catch-ups go on top
Example (2026, sole proprietor, age 45): $100,000 of net profit. SE tax is $14,129.55, so net earnings are $92,935.23. The employer piece is 20% of that, $18,587.05, and the employee deferral adds the full $24,500, for a total of $43,087.05, versus $18,587.05 in a SEP IRA.
Solo 401(k) limits
Limit
2026
2025
Employee elective deferral
$24,500
$23,500
Catch-up, age 50+
$8,000
$7,500
Catch-up, age 60–63
$11,250
$11,250
Total annual additions (excl. catch-up)
$72,000
$70,000
Compensation counted
$360,000
$350,000
Source: IRS annual retirement plan limit announcements. Once plan assets pass $250,000 you must file Form 5500-EZ each year.
Sole proprietor vs S corporation
S corp owners base everything on W-2 salary only, so a low salary limits the employer contribution even when profits are high. Sole proprietors base it on net profit after half of self-employment tax. Raising an S corp salary increases the 401(k) room but also payroll taxes, so run both numbers before changing pay.
Frequently asked questions
What is the solo 401(k) contribution limit for 2026?
Up to $72,000 in combined employee and employer contributions, plus catch-ups: $8,000 extra at age 50 or older, or $11,250 at ages 60 to 63. The employee deferral part is limited to $24,500. In 2025 the figures were $70,000, $23,500, $7,500 and $11,250.
How is the employer contribution calculated?
For an S corporation it is up to 25% of the owner's W-2 salary. For a sole proprietor or single-member LLC it works out to 20% of net self-employment profit after subtracting half of the self-employment tax, because the contribution itself reduces the compensation it is based on.
Is a solo 401(k) better than a SEP IRA?
It allows the same employer contribution as a SEP IRA plus the employee deferral, so it usually lets you save much more at low and middle incomes. For example, at $60,000 of net profit you might contribute about $11,000 to a SEP but over $35,000 to a solo 401(k). At very high incomes both hit the overall limit.
I have a 401(k) at my day job. Can I still open a solo 401(k)?
Yes. The employee deferral limit is shared across all your plans, so whatever you defer at work reduces the solo 401(k) deferral. The employer profit-sharing contribution to your own business plan is separate and still available.
What is the deadline for solo 401(k) contributions?
Employer contributions can be made up to your tax filing deadline, including extensions. Employee deferrals generally must be elected by December 31, although since 2023 a sole proprietor who opens a brand-new plan after year end can make first-year deferrals up to the original filing deadline.
Can solo 401(k) contributions be Roth?
Employee deferrals can be Roth if the plan allows it, and SECURE 2.0 also allows Roth employer contributions. Roth money is taxed now and grows tax-free. Starting in 2026, catch-up contributions by people whose prior-year FICA wages exceeded $150,000 must be Roth.
Who can open a solo 401(k)?
A business owner with no full-time employees other than a spouse. If you hire eligible employees, the plan must cover them and is no longer a one-participant plan.
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