Solo 401(k) for Self-Employed Spouses: 2026 Contribution Calculator
One spouse on a W-2; the other freelancing, consulting, or running a side business. The self-employed spouse has access to the most powerful retirement account most families overlook. Not financial or tax advice — your specific income and business structure matter.
2026 Solo 401(k) contribution limits
A Solo 401(k) — also called an individual 401(k) or self-employed 401(k) — has two independent contribution buckets for the self-employed participant, who acts as both employer and employee.
| Component | 2026 Limit | Notes |
|---|---|---|
| Employee elective deferral (base) | $24,500 | Subject to net SE compensation |
| Catch-up, ages 50–59 and 64+ | +$8,000 | → $32,500 total employee |
| Super catch-up, ages 60–63 | +$11,250 | → $35,750 total employee (SECURE 2.0) |
| Employer profit-sharing | 25% of net SE compensation | Employee + employer ≤ §415(c) cap |
| §415(c) annual additions cap | $72,000 | Catch-up contributions are above this cap |
| Maximum with 60–63 catch-up | $83,250 | $72,000 + $11,250 |
| Maximum with 50–59/64+ catch-up | $80,000 | $72,000 + $8,000 |
Sources: IRS Notice 2025-67 (2026 plan limits); IRS Rev. Proc. 2025-32; SECURE 2.0 Act §109 (super catch-up, ages 60–63).1
Solo 401(k) contribution calculator
Enter your net self-employment income (after business expenses, before SE tax) and your age. The calculator applies the 2026 SE tax formula (92.35% × 15.3% on the first $184,500 of net SE earnings, then 2.9% above) to find net SE compensation, then computes your maximum Solo 401(k) contribution and compares it to a SEP-IRA.
Solo 401(k) vs. SEP-IRA vs. SIMPLE IRA
For most self-employed spouses in dual-income households, the Solo 401(k) is the right choice. Here's why — and when the others might apply.
| Feature | Solo 401(k) | SEP-IRA | SIMPLE IRA |
|---|---|---|---|
| 2026 max contribution | $72,000 (+catch-up) | $72,000 | $18,100 (+catch-up) |
| Employee deferral component | Yes — $24,500 | No | Yes — $18,100 |
| Employer (profit-sharing) component | Yes — 25% of net SE comp | Yes — 25% of net SE comp | Employer match required |
| Advantage at lower SE income ($50K–$120K) | Strong — employee deferral dominates | Weak | Moderate |
| Advantage at higher SE income ($200K+) | Moderate (employer limit kicks in) | Approaches Solo 401k | Weak |
| Roth option | Yes (if plan document allows) | No | No |
| After-tax / mega backdoor | Yes (if plan document allows) | No | No |
| Loan provisions | Optional (plan document) | No | No |
| Requires employees? | No (owner + spouse only) | No | No (but structured for employees) |
| Plan setup deadline | December 31 of the plan year | Tax filing deadline (+ extensions) | October 1 for new plans |
| Complexity | Moderate (plan document required) | Simple | Moderate |
Rule of thumb: if net SE income is under $200K, a Solo 401(k) beats a SEP-IRA significantly. Above $200K, the gap narrows but the Roth option and mega backdoor access still favor the Solo 401(k) for most families.
Who qualifies for a Solo 401(k)
A Solo 401(k) is available to self-employed individuals with no full-time employees other than themselves and their spouse. That means:
- Sole proprietors (Schedule C filers)
- Single-member LLC owners with no W-2 employees
- Freelancers, consultants, and independent contractors
- Partners in a partnership (each partner opens their own)
- 1099 workers with a side business alongside a W-2 job
If the business brings on even one non-spouse full-time employee (1,000+ hours/year), the Solo 401(k) plan must be converted to a regular 401(k) and subjected to ERISA anti-discrimination testing. At that point, a SEP-IRA or SIMPLE IRA is often simpler.
How the contribution formula works
The two-bucket structure is what creates the Solo 401(k) advantage at moderate income levels:
- Net SE compensation: Start with net SE income (revenue minus business expenses). Subtract half of self-employment tax (12.4% SS on up to $184,500 of net SE earnings + 2.9% Medicare, with the employer-equivalent half deductible). This is your "net SE compensation" used in all contribution formulas.
- Employee deferral: You can defer up to $24,500 as the "employee" (or $32,500 at 50+; $35,750 at 60–63). This cannot exceed your net SE compensation but is not limited by a percentage formula.
- Employer profit-sharing: You contribute up to 25% of net SE compensation as the "employer" — capped so that employee base + employer ≤ $72,000.
- Tax deduction: Both components are pre-tax (or Roth if elected) — and the combined amount is deductible from gross income on Schedule 1, reducing your federal tax dollar-for-dollar.
Household contribution total: W-2 spouse + Solo 401(k) spouse
The two spouses' retirement plan limits are completely independent. The W-2 spouse can contribute up to $24,500 to their employer 401(k) (or $32,500/$35,750 at catch-up ages), and the self-employed spouse can contribute up to $72,000+ in their Solo 401(k) — simultaneously. The plans are separate; neither affects the other's limit.
A dual-income household where one spouse is self-employed with $150K net SE income and the other earns W-2 income could shelter the following in 2026 (both under 50):
- W-2 spouse 401(k): $24,500
- SE spouse Solo 401(k) (estimated): ~$59,000
- Combined: ~$83,500/year in pre-tax retirement contributions
That's before Roth IRAs, HSA contributions, or any 529 savings. Use the 401(k) vs. 529 prioritization calculator to see how this fits into your full household savings picture.
One exception: if the self-employed spouse also has a separate W-2 job, the employee deferral limit ($24,500) is shared across all plans they participate in that year. The employer profit-sharing component remains independent per plan.
Roth Solo 401(k) option
Most Solo 401(k) providers allow you to designate employee deferrals as Roth contributions at the time of election — meaning contributions are after-tax but growth and qualified withdrawals are tax-free. There's no income limit on Roth Solo 401(k) contributions (unlike Roth IRA, which phases out at $236,000–$246,000 MFJ in 2026).
The Roth vs. Traditional Solo 401(k) decision mirrors the same analysis as the Roth vs. Traditional 401(k) calculator — it depends on your current marginal rate vs. your expected retirement rate. For dual-income households in the 32%–35% bracket today who expect to be in 22%–24% in retirement, pre-tax often wins. For households earlier in their careers or doing Roth conversion planning, the Roth option preserves flexibility.
Note: starting 2026 under SECURE 2.0 high-earner rules, individuals earning above $145,000 in wages must make catch-up contributions as Roth — this applies to W-2 plans, not to self-employment catch-up contributions in a Solo 401(k), which remain elective.
Plan setup deadline: December 31
Unlike a SEP-IRA (which can be opened and funded up to the tax filing deadline including extensions), a Solo 401(k) plan document must be adopted by December 31 of the tax year in which you want to make contributions. You can fund the contribution up to the filing deadline, but the plan must exist before year-end.
If you're in Q4 and realized your spouse has self-employment income: open the Solo 401(k) now. Many major custodians (Fidelity, Schwab, Vanguard, TD Ameritrade) offer free prototype plan documents. The deadline is firm — missing it means waiting a full year or using a SEP-IRA instead.
QBI deduction coordination (§199A)
If your business generates Qualified Business Income under IRC §199A — now a permanent deduction per the One Big Beautiful Bill Act (OBBBA, July 2025) — the Solo 401(k) employer contribution reduces QBI dollar-for-dollar. A higher Solo 401(k) contribution may reduce your §199A deduction slightly. The net after-tax benefit still strongly favors maximizing the Solo 401(k) for most families, but a tax advisor can model the exact tradeoff at your income level and W-2 structure.
When to work with a fee-only advisor on Solo 401(k) planning
For a simple case — SE income under $100K, no employees, straightforward plan — the math is manageable and execution is a one-afternoon task at a major custodian. The complexity rises quickly when:
- The SE spouse also has a W-2 job (shared employee deferral, but separate employer contribution)
- You're exploring the mega backdoor Roth (after-tax contributions + in-service conversion within the Solo 401(k))
- The business is growing and part-time employees are on the horizon, requiring a plan conversion decision
- SE income fluctuates significantly year-to-year (SEP-IRA flexibility vs. Solo 401(k) efficiency tradeoff)
- You're coordinating Solo 401(k) with a defined benefit or cash balance plan for a higher-income SE spouse
- The household is also doing Roth conversions, IRMAA planning, or large 529 contributions — all of which interact with taxable income and plan contribution decisions
Fee-only planners who specialize in self-employed families model these interactions across both earners simultaneously — not just the 401(k) contribution in isolation. If the self-employed income is above $150K and there are multiple competing goals, the planning session typically pays for itself in the first year.
Get matched with a fee-only family financial planner
Solo 401(k) setup, household retirement optimization, and self-employment tax planning are exactly what fee-only family financial planners build into dual-income household plans.
- IRS Notice 2025-67 — 2026 Retirement Plan Limits. Employee elective deferral $24,500; §415(c) annual additions $72,000; catch-up $8,000 (50–59, 64+); super catch-up $11,250 (60–63); compensation limit $360,000. SECURE 2.0 §109 permanent changes effective 2025.
- Fidelity — Solo 401(k) Contribution Limits 2026. Confirms $24,500 employee deferral, $72,000 415(c) cap, catch-up and super catch-up amounts; employer profit-sharing formula; plan establishment deadline of December 31.
- IRS — One-Participant 401(k) Plans. Eligibility rules (no full-time employees other than spouse); contribution formula; plan document requirements; deadlines; spousal participation rules.
- SSA — Contribution and Benefit Base (SS Wage Base). 2026 Social Security wage base: $184,500. Used in SE tax calculation to determine the SS portion (12.4%) of self-employment tax, which in turn determines the half-SE-tax deduction and net SE compensation for 401(k) contribution purposes.
- IRA Financial — Solo 401(k) Contribution Limits 2025 & 2026. Cross-check of employee + employer formula, Roth option availability, mega backdoor access, and comparison table vs. SEP-IRA and SIMPLE IRA.
2026 Solo 401(k) limits ($24,500 employee, $72,000 §415(c)) confirmed per IRS Notice 2025-67 and Fidelity. SS wage base $184,500 per SSA.gov. SE tax formula (92.35% × 15.3%/2.9%) per IRS Schedule SE instructions. Calculator is an estimate; exact contribution requires Schedule SE calculation. Values current as of June 2026 — IRS announces annual adjustments each November.