Solo 401(k) or SEP IRA, What Is the Best Retirement Plan for a Solo Founder?
Solo 401(k) vs SEP IRA for a solo founder? For 2026, Solo 401(k) adds employee deferral ($24,500) on top of employer contribution up to $72,000 total — often the largest deduction. SEP IRA is simpler if you missed deferrals. Model limits, Roth, spouse, and timing here.
On this page
- Summary of What This Blog Covers
- Contribution Limits & Roth Options (2026)
- Spouse Participation & Payroll Timing
- Solo 401(k) — When It Wins
- SEP IRA — When It Wins
- Decision Checklist for Solo Founders
- Funding Calendar & Setup Checklist
- Book a Fractional CFO Strategy Session
- Frequently Asked Questions
Summary of What This Blog Covers
- Fast breakdown of contribution limits, Roth options, spouse participation, and payroll timing for a one-person business
- Clear “aha” moments so the rules click without a spreadsheet headache
- Practical scenarios, decision checklist, and five FAQs so you can act with confidence
Contribution Limits & Roth Options (2026)
Solo 401(k): employee deferral up to $24,500 + employer contribution up to 25% of comp → total $72,000 (or $80,000 if 50+ catch-up). Roth deferral available.
SEP IRA: employer-only, up to 25% of comp or $72,000 (no employee deferral, no Roth).
Spouse Participation & Payroll Timing
Solo 401(k): spouse can participate if bona fide employee (W-2 wages). Increases total contribution room.
SEP IRA: spouse treated as self-employed (no W-2 required).
Timing: Solo 401(k) deferral by Dec 31; employer by tax deadline. SEP by tax deadline (including extensions).
Solo 401(k) — When It Wins
Higher total limit ($72k vs SEP $72k but no deferral), Roth option, spouse participation, loan feature, earlier deadline for deferral. Best if you can afford employee deferral and want flexibility.
SEP IRA — When It Wins
Simpler setup, no annual commitment, deadline to tax filing (extensions), no payroll needed for spouse. Ideal if you missed deferral or want minimal paperwork.
Decision Checklist for Solo Founders (copy-paste)
☐ Projected profit & tax savings modeled
☐ Can I afford employee deferral by Dec 31?
☐ Want Roth option?
☐ Spouse participating?
☐ Need loan feature?
☐ Prefer simpler setup & later deadline?
☐ Multi-state or complex payroll?
Funding Calendar & Setup Checklist (copy-paste)
☐ Plan selected & documented
☐ Plan opened & funded (deferral by Dec 31 for Solo 401(k))
☐ Employer contribution scheduled (tax deadline)
☐ Spouse W-2 / participation set (if applicable)
☐ Roth election made (if desired)
☐ Payroll configured (Solo 401(k))
☐ Contribution receipt saved
Book a Fractional CFO Strategy Session
Insogna models limits, Roth choices, spouse participation, and payroll timing, then builds a funding calendar around your cash flow. We pick the right plan and lock in the savings. Whether you searched “tax preparer near me,” “Austin Texas CPA,” or “tax accountant near me,” contact us to decide with confidence and act this year.
Frequently Asked Questions
1) Can I do both Solo 401(k) and SEP IRA?
No — they are alternatives. Choose one per year. Solo 401(k) usually allows higher total contribution.
2) Spouse participation — do they need payroll?
Solo 401(k): yes, W-2 wages required. SEP IRA: no, treated as self-employed.
3) Roth option — which plan?
Solo 401(k) allows Roth deferral. SEP IRA does not (traditional only).
4) Deadline for employer contribution?
Both: tax filing deadline (including extensions). Solo 401(k) employee deferral: Dec 31.
5) Loan feature — only in Solo 401(k)?
Yes — Solo 401(k) allows loans up to $50k or 50% of balance. SEP IRA does not.