| Feature | Solo 401(k) | SEP-IRA |
|---|---|---|
| 2026 employee deferral | $24,500 | Not allowed |
| 2026 employer portion | Up to 25% of comp | Up to 25% of comp |
| 2026 total cap | $72,000 | $72,000 |
| Catch-up 50+ | $8,000 | None |
| Super catch-up 60-63 | $11,250 | None |
| Roth option | Yes (if plan allows) | Technically yes (SECURE 2.0) but rare |
| Plan loans | Up to $50,000 | No |
| Setup deadline for 2026 | Dec 31, 2026 | Tax day 2027 |
| Funding deadline | Tax day + extensions | Tax day + extensions |
| Form 5500-EZ | Once assets > $250k | Never |
| Employees allowed | Only spouse | SEP must include eligible employees |
Bottom line: Solo 401(k) wins on flexibility and total shelter at low-to-mid income levels. SEP-IRA wins on simplicity and no annual filing. At high income levels both reach the same $72,000 cap, but Solo still has Roth, catch-up, and loans.