What is a Solo 401(k)?
A Solo 401(k), also called a One-Participant 401(k), is a traditional 401(k) plan for self-employed individuals and business owners with no full-time employees. You can include your spouse in the plan.
There are two types of contributions you can make: elective deferrals and employer nonelective contributions.
What are elective deferrals?
Elective deferrals are contributions you make in lieu of salary. You can contribute up to the lesser of:
100% of: your compensation (if you’re a business owner) or your earned income (if you’re self-employed)
For 2025, $23,500 if you're 49 or younger or $31,000 if you’re 50 or older
Note: the limit is per person, not per plan, so the total of all elective deferrals from all plans can’t go over the limit.
What are employer nonelective contributions?
You can make employer nonelective contributions of up to 25% of your compensation as defined by your plan. For self-employed persons this compensation doesn’t include retirement plan contributions or the self-employment tax, which are deducted from your income. TurboTax will calculate these amounts for you (or tell you if you contributed too much to your Solo 401(k)).
What's my maximum contribution?
For 2025, for those age 50 and over there are various contribution amounts.
Ages 50–59: The total contribution limit is $77,500.
This is comprised of the $70,000 overall contribution limit and a $7,500 catch-up contribution.
Ages 60–63: The total contribution limit is $81,250.
This includes the $70,000 base limit and a special, higher catch-up contribution of $11,250.
Ages 64 and over: The total contribution limit is $77,500.
This is the same as the 50–59 age bracket, as they are eligible for the standard $7,500 catch-up contribution.
The deadline for company contributions is generally the tax filing deadline, which is April 15, 2026.
