The Solo 401(k): The Retirement Account Built for the One-Person Business
Most retirement accounts were designed with someone else in mind. Traditional pensions assumed lifelong employment. Workplace 401(k)s assume a company with HR and a plan administrator. Even the SEP IRA, popular as it is among the self-employed, has rules that can be less flexible.
The Solo 401(k) is different. It was built from the ground up for people who work for themselves, and for the right person, it can be one of the most effective retirement savings vehicles available.
Two Roles, Two Contribution Streams
Here is what makes the Solo 401(k) structurally unique: because you are both the owner and the worker in your business, the IRS allows you to contribute in both capacities. That dual structure is the engine behind the plan’s high limits.
As the employee, you can defer up to $24,500 of your income in 2026. As the employer, you can contribute an additional 25% of W-2 compensation (or roughly 20% of net self-employment income for sole proprietors). Combined, this allows for total contributions of up to $72,000 for the year.
In practice, this allows a self-employed person with moderate income to build retirement savings more efficiently with a Solo 401(k) than many other retirement options. A SEP IRA, for example, is based entirely on a percentage of income. At lower income levels, that percentage math can leave a significant gap between what you are allowed to save and what you could otherwise contribute. The Solo 401(k)’s flat employee deferral closes that gap.
The Catch-Up Advantage
If you are 50 or older, the Solo 401(k) offers something no SEP IRA can: catch-up contributions. In 2026, that adds $8,000 on top of the standard employee deferral, pushing the total possible contribution to $80,000 for eligible participants. For clients in their peak earning years who are accelerating retirement savings, this is a meaningful difference.
A Roth Option That Many People Miss
Many Solo 401(k) plans allow you to designate your employee deferrals as Roth contributions, meaning you contribute after-tax dollars that grow and can eventually be withdrawn completely tax-free. This is one of the most underutilized features of the plan.
Not all SEP IRA’s and SIMPLE IRA’s offer this option. The Solo 401(k) stands nearly alone among high-limit retirement accounts in offering a built-in Roth path without requiring a conversion or a separate account.
For younger self-employed professionals, or anyone who expects their tax rate to rise over time, the ability to lock in today’s rate on a large annual contribution is worth serious consideration.
The One Deadline You Cannot Afford to Miss
This is where the Solo 401(k) requires more attention than a SEP IRA. To make employee deferrals for a given tax year, the plan must be established by December 31st of that year. You cannot open one in March during tax season and make deferrals retroactively the way you can with a SEP IRA.
Employer contributions have more flexibility and can be made up to your tax filing deadline, including extensions. But the window for employee deferrals closes at year end, full stop. If a Solo 401(k) is something you want for 2026, the time to act is before the calendar turns.
Who It Is Not For
The Solo 401(k) has one firm boundary: it is not available to businesses with full-time employees other than the owner and their spouse. The moment you bring on a qualifying employee, you will need a different plan structure. For business owners who anticipate hiring, this is worth factoring into your long-term planning now rather than discovering it later and dealing with the hassle of changing plans.
Is It Worth the Setup?
Compared to a SEP IRA, the Solo 401(k) does require slightly more paperwork upfront, and once your plan assets exceed $250,000 you will need to file Form 5500 annually with the IRS. For most business owners, that is a modest administrative cost relative to the benefits.
The question worth asking is not whether the Solo 401(k) is complicated. It is whether the combination of higher effective limits at moderate incomes, catch-up contributions, and a Roth option makes it a better fit for where you are now and where you are headed.
At Legacy, that is exactly the kind of question we help clients work through. If you are self-employed and questioning whether your current strategy is as effective as it could be, now is a good time to evaluate your options.
