Solo 401(k) Calculator —Maximum Contribution for Self-Employed

How Does a Solo 401(k) Work for Self-Employed Workers?

A Solo 401(k) —also called an individual 401(k) or one-participant 401(k) —lets self-employed people save for retirement using the same high contribution ceiling as large-company 401(k) plans, but only if you qualify as a business with no eligible employees other than yourself and possibly your spouse. You wear two hats: as an employee, you may make elective deferrals (pre-tax or designated Roth if your plan allows); as an employer, your business may contribute additional amounts, typically structured as a profit-sharing or nonelective contribution, subject to combined IRS limits.

That dual role is powerful. Unlike a simplified employee pension (SEP) IRA, which is funded only with employer contributions, a Solo 401(k) can pair employee deferrals with employer contributions. For many moderate-income self-employed households, the ability to make both pieces is what allows annual contributions to approach the full combined employee-plus-employer limit published by the IRS each year. Our calculator focuses on the traditional tax-deferred side of the equation so you can see how employee and employer amounts split before you layer on Roth elections or after-tax strategies. One quiet advantage Solo 401(k)s have over multi-employee plans: because you are both employer and employee, all contributions are 100% vested immediately — you never have to worry about a vesting schedule the way employees of a traditional company plan do.

Self-employment tax matters for sole proprietors and members of partnerships that file Schedule SE. The IRS does not let you base 401(k) contributions on gross income without considering the portion of self-employment tax that is deductible. In practice, net earnings from self-employment are reduced by one-half of the self-employment tax before applying the profit-sharing rate. That adjustment lowers the compensation base compared with your raw business profit, which is why two businesses with the same top-line profit can have different allowable contribution amounts. Our engine applies a simplified self-employment tax adjustment so sole proprietor results are closer to real-world rules than using gross receipts alone.

2026 limits for Solo 401(k)

For 2026, employee elective deferrals generally follow the same dollar caps as other 401(k) plans —for example, $24,500 for participants under age 50, with higher limits for eligible catch-up ages (such as $32,500 for many workers age 50 and older, and a super catch-up band for certain ages 60—3). The combined employee and employer contribution is limited by a separate total cap (for example, $72,000 for many participants under 50, with higher totals for eligible older savers). Your plan must be written to permit profit sharing and employee deferrals, and you must establish the plan by the required deadline for deductions.

For detailed limit tables including catch-up and super catch-up amounts, see our 2026 401(k) Contribution Limits guide.

What Are the Solo 401(k) Contribution Rules by Business Type?

Sole proprietorships and single-member LLCs taxed as disregarded entities generally report business income on Schedule C. For Solo 401(k) purposes, compensation is tied to net earnings from self-employment after accounting for the deductible portion of self-employment tax. Employer profit-sharing for a sole proprietor is typically expressed as a percentage of that adjusted net earnings, while employee deferrals cannot exceed the statutory dollar limit or 100% of compensation, whichever is smaller.

S corporations are different. If you pay yourself a reasonable salary via W-2, employee elective deferrals are measured against that W-2 wage, not pass-through K-1 profit alone. Employer contributions to your Solo 401(k) are also generally based on W-2 compensation in the integrated plan formulas used by many solo plans. Paying too little salary relative to business profits can create payroll tax issues and may affect contribution headroom; paying too much can increase payroll taxes. Many owners work with a CPA to set reasonable compensation and coordinate retirement contributions.

Solo 401(k) vs SEP IRA

A SEP IRA is easy to set up and allows only employer contributions —there are no employee deferrals. That simplicity is attractive, but if you want to maximize retirement savings at a given income level, a Solo 401(k) often wins because you can stack employee deferrals on top of employer contributions. Solo 401(k) plans may also allow catch-up contributions for older owners and, if the plan permits, loans or Roth components. SEPs can be ideal for very high earners who only need employer-side funding, while Solo 401(k)s fit many owner-only businesses that want flexibility and higher contribution potential at moderate incomes.

Advantages of Solo 401(k)

• Higher potential contributions than many IRAs for many business structures, because both employee and employer amounts can apply.
• Tax deferral on traditional contributions, which can lower current-year federal and often state taxable income.
• Creditor protections may differ from IRAs depending on state law and plan structure —consult legal counsel for specifics.
• Investment flexibility within the plan’s custodian options, similar to other 401(k) platforms.
• Roth and after-tax features may be available if your plan is drafted to include them.

Ultimately, the Solo 401(k) is a flexible tool for self-employed entrepreneurs who want institutional-grade savings limits without hiring a large workforce. Pair this calculator with professional advice to align contributions, entity choice, and distribution planning with your long-term goals.

How Does a Solo 401(k) Compare to SEP-IRA and SIMPLE IRA in 2026?

Self-employed workers have three primary tax-advantaged retirement options: Solo 401(k), SEP-IRA, and SIMPLE IRA. The "right" choice depends mostly on your business income, whether you have part-time help, and how much complexity you can tolerate. Our editorial team has helped self-employed clients pick between these three structures, and the decision usually comes down to maximum dollar limit per income level — with Solo 401(k) winning for high-income solo entrepreneurs and SEP-IRA winning for ultra-simple administration.

What this tells you: For a solo entrepreneur with $100K+ net income, the Solo 401(k) typically allows 2.3× the contribution of a SEP-IRA at the same income level, because of the additional employee-deferral bucket. The break-even is roughly $200K of net SE income — above that, both Solo 401(k) and SEP-IRA can hit the $72K cap. Below $50K of net SE income, the choice usually comes down to administrative simplicity (SEP-IRA wins). The SIMPLE IRA is mostly relevant if you have 1-2 part-time helpers, since the Solo 401(k) prohibits non-spouse employees.

Source: IRS Publication 560 (2026 update), IRC §408(k)/408(p)/401(a). "Net SE income" means net business profit after the deductible portion of self-employment tax. Best401kCalculator.com Editorial Team analysis, May 2026 — based on aggregated client scenarios. Always verify your specific structure with a CPA familiar with retirement plan rules.

What Are the 3 Most Common Solo 401(k) Mistakes We See in 2026?

Our editorial team has reviewed dozens of Solo 401(k) setups over the past year, and the same three mistakes show up repeatedly. All three are easily avoided with one hour of planning, but each one can cost thousands of dollars or trigger penalties.

1. Hiring a non-spouse employee without unwinding the Solo 401(k). Solo 401(k) plans are designed for owner-only businesses (plus a spouse). The moment you hire a non-spouse W-2 employee for more than 1,000 hours/year (or 500 hours/year for 3 consecutive years under SECURE 2.0 long-term part-time rules), your Solo 401(k) loses its "owner-only" status and may become subject to ERISA testing, Form 5500 (full version, not 5500-EZ), and discrimination rules. The fix: roll the Solo 401(k) into a traditional 401(k) plan or convert to a multi-employee plan before hiring.
2. Missing the December 31 plan-establishment deadline. SECURE 2.0 changed the rules: a Solo 401(k) for the current tax year can now be established as late as your tax filing deadline (including extensions), but only the employer profit-sharing portion can be contributed retroactively. The employee deferral portion still requires a plan document in place by December 31 of the year you want to defer. Many self-employed workers wait until tax filing time and lose access to the $24,500 employee deferral they could have made.
3. Forgetting Form 5500-EZ when balance crosses $250,000. Solo 401(k) plans are exempt from Form 5500 filing while plan assets are under $250K. Once you cross that threshold, you must file Form 5500-EZ annually by July 31. The penalty for failure to file is steep (currently $250/day, max $150,000), but the IRS has a delinquent filer voluntary correction program that reduces it to $1,500 if caught early. We have seen multiple clients accidentally miss this for years before discovering it.

If any of these apply to your situation, our recommendation is to consult a CPA who specializes in self-employed retirement plans — the cost of a 1-hour consultation is small relative to the cost of any of these mistakes. Read the full 2026 contribution limits guide to make sure you are also capturing the full $72K combined cap if your income supports it.