Solo 401(k) Contribution Calculator

2026 rules

Find the most you can put into a Solo 401(k) for 2026 as a sole proprietor or S corp owner.

Your numbers

Business type

Net profit (Schedule C) or your W-2 salary from the S corp

Your age at the end of 2026

401(k) deferrals at another job this year

The $24,500 employee limit is shared across all plans.

Result

Maximum 2026 Solo 401(k) contribution$46,804

Net earnings after half of SE tax$111,522
Employee deferral$24,500
Employer contribution (20% of net earnings)$22,304
Total$46,804
Cap (section 415, plus catch-up)$72,000

Employee deferrals for a sole proprietor are due by the tax-filing deadline but must be elected by Dec 31. Employer contributions can wait until the extended due date.

How it works

You contribute twice. As the employee you can defer up to $24,500, plus $8,000 at 50 or older, or $11,250 if you're 60 to 63. As the employer you add up to 20% of net self-employment earnings (25% of W-2 pay if you run an S corp).

For a sole proprietor, net earnings are your Schedule C profit minus half your self-employment tax. Everything except catch-ups is capped at $72,000.

The employee limit is per person across all plans, so deferrals at a day job reduce it. The employer share is separate for each unrelated business.

2026 figures: IRS Rev. Proc. 2025-32 (2026 inflation adjustments); IRS Notice 2025-67 (2026 retirement plan limits); SSA 2026 COLA fact sheet; IRS Notice 2026-10 and Announcement 2026-11 (mileage).

Questions

Can I make Roth contributions to a Solo 401(k)?

Yes, if the plan allows. Employee deferrals can be Roth, and SECURE 2.0 also lets plans offer Roth employer contributions.

When do I need to file Form 5500-EZ?

Once plan assets pass $250,000 at the end of a year, file Form 5500-EZ by July 31 of the following year.