What Is a Solo 401(k) for Self-Employed Workers?
Working for yourself means losing the retirement plan that came automatically with a job, but it doesn’t mean losing access to a workplace-style plan altogether. A solo 401(k) is built specifically for people who run their own business with no employees other than a spouse.
The short answer
A solo 401(k), sometimes called an individual or one-participant 401(k), is a retirement plan designed for self-employed people and small business owners with no employees besides themselves and possibly a spouse. It works like a standard employer 401(k), but because the business owner sits on both sides of the plan, they can contribute in two separate capacities — as the “employee” and as the “employer” — which can allow for higher total contributions than a typical wage-earner’s plan alone.
Why the two contribution roles matter
In a solo 401(k), the same person wears two hats. As the employee, they can defer a portion of their compensation into the plan, similar to how a worker at a company defers part of a paycheck. As the employer, the business itself can also contribute a percentage of the owner’s compensation or net self-employment earnings, functioning like a profit-sharing contribution a company might otherwise make on an employee’s behalf. Because both contribution types flow into the same account, a self-employed person can end up setting aside considerably more than they could through a personal IRA alone, though the exact math depends on income, business structure, and current contribution rules, which are set by the government and change over time.
Traditional or Roth, and other plan choices
Many solo 401(k) providers offer both traditional and Roth versions for the employee-deferral portion, similar to the choice between a traditional and Roth IRA — pre-tax now with taxable withdrawals later, or taxed now with tax-free qualified withdrawals later. Some providers also allow after-tax contributions above the standard limits, which for certain solo plans opens the door to a version of the strategy known as a mega backdoor Roth, though not every solo 401(k) provider supports this. The employer-side profit-sharing contribution, by contrast, is typically pre-tax regardless of which option is chosen for the employee side, so it’s worth understanding how a specific provider structures the plan before assuming it works exactly like a Roth IRA.
A common point of confusion
People sometimes assume a solo 401(k) is only for full-time freelancers, but it’s generally available to anyone with self-employment income, even someone who also holds a regular job and has income on the side from consulting, freelancing, or a small business. Another point of confusion is the “no employees” rule — the plan is designed for business owners without common-law employees, though a spouse who also works in the business can typically participate too. Once a business hires even one non-spouse employee who meets eligibility requirements, the solo structure generally no longer fits, and the business may need to consider a different type of plan that covers the wider workforce, since retirement plans with employees carry additional administrative and compliance requirements that a one-person plan doesn’t.
Setting one up and keeping it running
Solo 401(k) plans are typically opened through a brokerage or plan provider rather than through an employer’s HR department, since the business owner is effectively both. There’s usually a plan document to adopt, an account to open, and — once plan assets grow past a certain size — an annual filing requirement that smaller plans are exempt from. None of this is especially complicated compared with running payroll for a team, but it does put the administrative responsibility on the business owner rather than an employer’s benefits department, which is worth planning for at tax time.
The bottom line
A solo 401(k) exists to give self-employed people a plan that can hold meaningfully more than an IRA by letting the same person contribute as both employee and employer. The right fit depends on business structure, income, and whether the business ever expects to hire, so it’s worth revisiting the plan’s setup periodically rather than assuming it stays a fit forever.