Solo 401(k) for Self-Employed Workers
A Solo 401(k), also called a one-participant 401(k), is designed for a business owner with no common-law employees other than a spouse. It can be powerful because the owner may contribute in both employee and employer capacities, but the plan also carries administrative responsibilities that should not be ignored.
Use this page to understand the structure and decision points. For current contribution limits, deadlines and filing requirements, verify the latest IRS guidance rather than relying on an evergreen number embedded in an article.
Who should evaluate a Solo 401(k)?
Owner-only businesses with stable self-employment income are the most obvious candidates. The structure can be especially relevant when an owner wants contribution flexibility, potential Roth features or plan options that a simple IRA arrangement may not provide.
The employee rule is critical. If the business adds eligible common-law employees, the plan may no longer qualify as a one-participant 401(k) and the compliance picture changes.
Understand the two contribution roles
The owner can generally participate as both employee and employer, subject to current law and plan terms. That is one reason a Solo 401(k) can differ from a SEP at the same level of business profit. The exact calculation can be more complex for self-employed individuals because net earnings and deductible self-employment tax affect plan compensation.
Compare providers on plan features, not only price
Ask whether the plan supports Roth contributions, rollovers, loans, brokerage access, automatic investing and the administrative documents you may need. Also ask what happens when plan assets cross reporting thresholds or when the business hires employees.
A low-cost provider can still be a poor fit if the plan document does not support the feature you expect to use.
Connect the account to the retirement target
The account structure is useful only if the contribution plan closes the retirement gap. Calculate the amount you need to save, then test whether that contribution is realistic within business cash flow and current plan rules.
Calculate My Retirement Number
Know the savings target before you decide how aggressively to fund the account.
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Frequently asked questions
Can my spouse participate in my Solo 401(k)?
A spouse who legitimately works in the business may be able to participate, subject to compensation and plan rules. Verify the details with the plan provider and tax professional.
What happens if I hire employees?
The plan may need to change because a one-participant 401(k) is generally for an owner-only business and spouse. Employee eligibility should be reviewed promptly.
Is a Solo 401(k) better than a SEP IRA?
Sometimes, but not always. Compare contribution mechanics, employees, Roth availability, administration, fees and the desired contribution level.