Owner-Only 401(k) Calculator 2026
Calculate your maximum Solo 401(k) contribution as a self-employed owner. Combines the $23,500 employee deferral with the 20%/25% employer profit-sharing, up to the $70,000 total annual additions limit — plus catch-up if age 50+.
The Solo 401(k) Two-Bucket Contribution Limit
The Solo 401(k) (also called Owner-Only 401(k), One-Participant 401(k), or Solo-k) is the most powerful retirement plan for self-employed individuals with no W-2 employees other than themselves and their spouse. For 2026, the contribution limit is structured as two separate buckets that combine: the employee elective deferral of $23,500 (plus $7,500 catch-up if age 50+, or $11,250 super catch-up if age 60-63 per SECURE 2.0), and the employer profit-sharing contribution of up to 25% of compensation. The total combined limit per individual is $70,000 for 2026 (or $77,500 with catch-up, $81,250 with super catch-up). Per IRS guidance on One-Participant 401(k) Plans, the employer side is capped at 20% of net self-employment earnings (after the 50% SE tax deduction) for sole proprietors, or 25% of W-2 wages for S-corp owners.
Sole Proprietor vs S-Corp — The Math Difference
The math for the employer profit-sharing differs by entity. Sole proprietors: net Schedule C earnings × 0.9235 (SE tax adjustment) × 0.20 (the effective 20% rate after factoring in the SE tax deduction). S-corp owners: W-2 wages × 0.25. The S-corp formula produces a larger employer contribution at lower compensation levels, but the S-corp owner must pay the additional payroll taxes on those W-2 wages. Example: $100,000 in net SE earnings as sole prop gives an employer contribution of $100,000 × 0.9235 × 0.20 = $18,470. The same income as $100,000 W-2 wages in an S-corp gives $100,000 × 0.25 = $25,000 employer contribution — a $6,500 difference, but the S-corp owner paid $7,650 in FICA on those wages. The break-even depends on your other distributions vs wages mix.
Spouse Eligibility — Effectively Doubling the Contribution
If your spouse works in the business and is paid wages or has SE earnings, they can maintain their own employee deferral + employer contribution under the same Solo 401(k) plan document. This effectively doubles the household contribution to a maximum of $140,000 for 2026 (or $155,000 with both age 50+ catch-up, $162,500 with both at the super catch-up age 60-63). The spouse must actually perform work in the business — paper-only employment is a red flag for IRS scrutiny. Both employee deferrals and employer contributions count against the individual $70,000 cap, not a combined household cap. This is the Solo 401(k)'s biggest advantage over a SEP-IRA, which only allows employer contributions and has no spouse-doubling option without a separate plan.
2026 Catch-Up Changes — Roth Mandate for High Earners
SECURE 2.0 added a super catch-up of $11,250 for ages 60-63, available 2025+. For 2026, this combines with the regular $7,500 catch-up rules — ages 50-59 get $7,500 catch-up, ages 60-63 get $11,250, and ages 64+ revert to $7,500. A more controversial 2026 change: high-earner catch-up contributions (for those earning more than $145,000 in W-2 wages in the prior year) must be Roth — the pre-tax catch-up is no longer allowed. This rule was delayed from 2024 to 2026 by IRS Notice 2023-62, and forces high earners into the Roth bucket whether they want it or not. Source: IRS 401(k) contribution limits. Last updated May 2026.
Frequently Asked Questions
What is the 2026 Solo 401(k) contribution limit?
For 2026: employee deferral of $23,500 + employer profit-sharing up to 20% of net SE earnings (sole prop) or 25% of W-2 wages (S-corp), with a combined cap of $70,000 per individual. Add $7,500 catch-up at 50+, or $11,250 super catch-up at age 60-63 under SECURE 2.0.
Do I need to have no employees to use a Solo 401(k)?
You can only have your spouse as an employee. Any other W-2 employee (full-time, part-time over 1,000 hours, or 3 consecutive years over 500 hours under SECURE 2.0) makes the plan ineligible. If you hire your first non-spouse employee, you must convert to a SIMPLE IRA or full 401(k) within reasonable time.
Solo 401(k) vs SEP IRA — which is better?
Solo 401(k) is almost always better: it allows employee deferrals (SEP does not), allows Roth contributions (SEP cannot before 2026 changes), permits loans up to $50,000, and allows spouse to contribute their own employee deferral. SEP IRA only beats Solo 401(k) when paperwork simplicity matters more than maximum contribution.
When do I have to set up a Solo 401(k)?
For 2026 employee deferrals, the plan must be adopted by December 31, 2026. For employer contributions only (no employee deferral), SECURE Act 2019 allows establishing the plan up to your tax filing deadline including extensions (October 15, 2027 for a 2026 contribution). Either way, contributions can be funded by the tax-filing deadline plus extensions.
Can my spouse contribute to my Solo 401(k)?
Yes, if your spouse is a W-2 employee or has self-employment earnings in the business. They contribute under their own $70,000 cap. Both spouses age 50+ can max at $77,500 each, or $81,250 each if both are in the 60-63 super catch-up age window — totaling up to $162,500 per household.
What is the Roth Solo 401(k) catch-up mandate?
Starting 2026 (delayed from 2024 by IRS Notice 2023-62), catch-up contributions for high earners (prior-year W-2 wages above $145,000, indexed) must be Roth, not pre-tax. Self-employed sole proprietors are technically exempt because they don't have prior-year W-2 wages, but S-corp owners must comply if their W-2 wages from the S-corp exceeded the threshold.