Solo 401(k) Catch-Up Contributions After 50: The $8,000 a SEP IRA Can't Match
Here is the short version of the solo 401(k) vs SEP IRA debate for anyone over 50: the SEP IRA has no catch-up contributions. Zero. At any age. The solo 401(k) gives you $8,000 of extra deferral room at 50 and up, and $11,250 at 60 through 63. That one structural difference is worth more than most of the fee and flexibility arguments that dominate this comparison. I have watched people agonize over expense ratios while leaving five figures of catch-up room on the table, and it is almost always because nobody told them the SEP cannot do this at all.
Catch-up contributions to a solo 401(k): the 2026 numbers
A solo 401(k) is a 401(k) in the IRS's eyes, so the same limits apply. For 2026: the base employee deferral is $24,500. At age 50 or older you add an $8,000 catch-up for a total deferral of $32,500. At ages 60 through 63, SECURE 2.0 allows a "super catch-up" of $11,250 instead, for $35,750 of deferral, but only if your plan document adopted that provision. Catch-up money sits on top of the $72,000 annual additions cap, so the real ceiling for a 55-year-old is $80,000 in one plan, not $72,000.
The SEP side of the comparison is brutally simple. A SEP IRA accepts only employer contributions, capped at 25% of compensation (20% of net self-employment income for a sole proprietor). There is no employee deferral, which means there is nothing to catch up on. The IRS does not allow catch-up contributions to a SEP at any age.
A worked example: 55 years old, $150,000 of self-employment income
Take a 55-year-old freelance consultant with $150,000 of net self-employment income. Under a SEP IRA, the contribution is roughly 20% of that net income, about $28,000 after the self-employment tax adjustment. Age changes nothing.
Under a solo 401(k), the same person contributes the $24,500 employee deferral, plus the $8,000 catch-up, plus the same ~$28,000 employer contribution. Total: about $60,500. The difference between the plans is $32,500 a year, and almost all of it is the employee deferral and catch-up that the SEP structurally cannot offer. For a married couple where both spouses participate, double the catch-up: two 50+ participants add $16,000 of extra room in a single plan.
Decision rules: when the catch-up decides the plan
If you are under 50, the catch-up is irrelevant and the comparison comes down to the usual deferral math. If you are 50 to 59, the solo 401(k) starts every comparison $8,000 ahead, before a single other factor is considered. If you are 60 to 63, check whether your plan document adopted the super catch-up; if it did, the lead is $11,250.
The one case where the catch-up does not matter: if your earnings are too low to use the room. Catch-up contributions are extra deferral capacity, not extra income. A part-time consultant netting $40,000 cannot stuff $32,500 into a plan regardless of age. The catch-up only helps when you have enough compensation to fund it.
Over 50 and choosing a plan?
Run your own income through both plans, catch-up included.
Run your own numbers with the free calculatorFrequently asked questions
Can you make catch-up contributions to a solo 401(k)?
Yes. The solo 401(k) follows standard 401(k) catch-up rules: $8,000 in 2026 at age 50+, or $11,250 at ages 60 through 63 if your plan adopted the SECURE 2.0 super catch-up. Catch-ups sit on top of the $72,000 annual additions limit.
Can you make catch-up contributions to a SEP IRA?
No. SEP IRAs accept only employer contributions, with no employee deferral component, so there is no catch-up provision at any age. The extra $8,000 to $11,250 is available only inside a 401(k) structure.
Do catch-up contributions have to be Roth in 2026?
If your prior-year FICA wages exceeded $150,000, catch-ups must go to a Roth account under SECURE 2.0, and 2026 is the first year the rule applies. Below that threshold you can choose pre-tax or Roth.
Does my plan document need to allow catch-ups?
Yes. Catch-ups are only permitted if the plan document allows them. Most major-brokerage solo 401(k) documents include the standard catch-up; the 60-63 super catch-up needs separate adoption. Confirm with your provider.
Can both spouses make catch-up contributions to one solo 401(k)?
Yes, if both spouses participate in the plan. Each gets a catch-up allowance based on their own age, so two 50+ participants add $16,000 of extra deferral room in 2026.
Related: Solo 401(k) Roth vs Traditional: The One Number That Decides It · Hiring Your Spouse in a Solo 401(k): The Double-Contribution Rules · Solo 401(k) vs SEP IRA for S-Corp Owners · Solo 401(k) Limits When You Also Have a W-2 Job With a 401(k)
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