Which of the 2 Retirement Plans Lower Taxes the Most This Year? Solo 401(k) or SEP IRA?
The largest tax cut you control this year isn’t a deduction — it’s choosing the right retirement plan. Solo 401(k) usually wins for bigger deductions; SEP shines for deadline flexibility.
Summary of What This Blog Covers
- Side-by-side Solo 401(k) vs SEP IRA for 30-year-old entrepreneurs
- Limits, deadlines, owner-employee nuances, cash-flow impact
- Step-by-step plan to capture the biggest deduction this year
The 60-Second Verdict
Solo 401(k) = employee deferral + employer contribution → usually bigger deduction this year.
SEP IRA = employer-only → simpler, fundable by extension.
2025 Contribution Limits
Solo 401(k): $23,500 employee deferral + up to 25% employer → $70,000 max (under 50).
SEP IRA: Up to 25% employer → $70,000 max.
Deadlines & Setup Timing
Solo 401(k): Establish by 12/31, employee deferral by final payroll, employer by filing.
SEP IRA: Establish & fund by filing deadline (including extensions).
Quick Math Comparison
$150k profit, $60k salary → Solo 401(k) ~$52k total contribution vs SEP ~$37.5k. Solo wins by ~$14.5k deduction.
When Solo 401(k) Wins
Higher profit, can defer pay, want Roth option, planning backdoor Roth (no pro-rata).
When SEP IRA Wins
Late in year, missed payroll setup, simpler administration, no employees yet.
Roth Considerations
Solo 401(k) offers Roth deferrals. SEP does not. Roth = pay tax now, grow tax-free.
Your Year-End Checklist (copy-paste)
☐ Run profit projection
☐ Choose plan (Solo 401(k)/SEP)
☐ Establish Solo 401(k) by 12/31 if needed
☐ Set payroll deferral %
☐ Schedule employer contribution
☐ Document reasonable salary if S Corp
Book Your Contribution Strategy
Insogna models Solo 401(k) vs SEP against your exact numbers, sets deadlines, provides paperwork, and coordinates payroll. Whether you searched “tax preparer near me for retirement plans,” “Austin Texas CPA for Solo 401k,” or “SEP IRA help,” we turn the biggest deduction into reality this year.
Frequently Asked Questions
1) Can I have both plans?
No — limits are combined. Pick one.
2) Do I need employees to use Solo 401(k)?
No — perfect for owner-only businesses.
3) Roth Solo 401(k) or traditional?
Lower bracket now → Roth. Higher bracket → traditional deferral.
4) How does S Corp salary affect this?
Salary fuels employee deferral. Higher reasonable salary = bigger Solo 401(k) total.
5) Backdoor Roth conflict?
SEP counts in pro-rata rule. Solo 401(k) does not — many keep IRAs at zero.