The solo 401(k) is one of the most powerful retirement savings tools available to self-employed business owners—and it's dramatically underutilized. If you're self-employed with no employees (other than a spouse), this retirement plan deserves serious consideration. It offers contribution limits that rival corporate executive packages, and the tax benefits are substantial.
Let's start with the basics. A solo 401(k) is simply a 401(k) plan that covers only one person—the business owner. Because there's no need to include employees, the plan can be structured with features unavailable in traditional 401(k)s, including the ability to make profit-sharing contributions that escape payroll taxes entirely.
The contribution limits for 2024 are generous. As an employee, you can contribute up to $23,000 in salary deferrals (the same as a regular 401(k)). But as an employer, you can also make profit-sharing contributions of up to 25% of your net self-employment income. Combined, this can total over $50,000 per year in tax-deductible contributions—and if you're 50 or older, you get an additional $7,500 catch-up contribution, bringing the potential total to over $60,000.
Let's work through an example. Say you're a consultant with $200,000 in net self-employment income. As an employee, you defer $23,000. Your profit-sharing contribution is calculated as 25% of your net income minus the self-employment tax deduction. Roughly, you could add another $40,000-$45,000 in employer contributions. That's a potential $63,000 to $68,000 in total contributions—all tax-deductible.
The tax benefits are two-fold. First, your contributions reduce your taxable income, lowering your income tax bill. Second, and often overlooked, contributions as an employer (profit-sharing) reduce your self-employment tax. The IRS allows you to deduct half of your self-employment tax from your gross income when calculating your adjusted gross income (AGI). But profit-sharing contributions go further—they reduce the net self-employment income that the tax is calculated on.
There's a Roth option too. You can make Roth contributions to your solo 401(k), allowing your money to grow tax-free forever. While you don't get an immediate deduction for Roth contributions, qualified withdrawals in retirement are completely tax-free. For high earners who expect to be in a similar or higher tax bracket in retirement, the Roth option is compelling.
Another advantage of solo 401(k)s is the loan feature. You can borrow up to 50% of your account balance (maximum $50,000) as a loan from your own plan. This can be useful for business emergencies or major personal expenses, though the rules around plan loans are strict and must be followed carefully.
Setting up a solo 401(k) is straightforward. You can open an account with any major brokerage—Fidelity, Vanguard, Schwab, and others offer solo 401(k) plans with no account fees. You'll need an Employer Identification Number (EIN) for the account, which is free to obtain from the IRS. The plan must be established by December 31 to take effect for that year, though contributions can be made until your tax filing deadline (typically April 15).
One common mistake is not maximizing contributions. Many solo 401(k) holders contribute only the employee portion ($23,000) but forget the employer profit-sharing contribution. If you have a good year, maxing out the profit-sharing contribution can dramatically accelerate your retirement savings and reduce your tax bill at the same time.
There's also the "true-up" provision. If you're self-employed with uneven cash flow (common for consultants and contractors), you can make larger contributions in high-income months and smaller ones in low-income months. As long as the total for the year doesn't exceed the annual limits, you're fine.
A solo 401(k) works exceptionally well when combined with an S-Corp election. The S-Corp allows you to reduce self-employment tax on a portion of your income, and the solo 401(k) lets you redirect those tax savings into tax-deferred retirement savings. The combination is powerful.
If you're self-employed and not currently maximizing a retirement plan, start researching your options today. The solo 401(k) offers unmatched flexibility and contribution limits for the self-employed. With proper planning, you can build substantial retirement savings while reducing your current tax burden.