What Is a Solo 401(k)? The Best Retirement Account for Self-Employed People

A Solo 401(k) — also called an Individual 401(k) or Self-Employed 401(k) — is a retirement account designed for business owners with no full-time employees other than a spouse. It offers the highest contribution limits of any retirement account available to self-employed individuals, often allowing six-figure annual contributions.

Who Qualifies for a Solo 401(k)

You qualify if you have self-employment income and no full-time W-2 employees (other than your spouse). This includes freelancers, independent contractors, consultants, sole proprietors, LLC owners, and side-hustlers with 1099 income. You can have a Solo 401(k) even if you also have a regular W-2 job.

Solo 401(k) Contribution Limits (2025)

The Solo 401(k) allows contributions in two capacities:

• Employee contributions: Up to $23,500 (or $31,000 if age 50+), same as a regular 401(k)
• Employer contributions: Up to 25% of net self-employment income
• Combined limit: Up to $70,000 total ($77,500 if 50+)

Example: If you earn $100,000 in self-employment income, you can contribute $23,500 as employee + $18,587 as employer (25% of net self-employment income after SE tax deduction) = $42,087 total. This is far more than the $7,000 IRA limit.

Traditional vs. Roth Solo 401(k)

Like regular 401(k)s, Solo 401(k)s come in two flavors:

• Traditional: Contributions reduce taxable income now; you pay taxes on withdrawals in retirement
• Roth: Contributions from after-tax dollars; growth and withdrawals are tax-free in retirement

Many providers offer both options within the same Solo 401(k). High earners in their peak years often prefer Traditional; younger earners or those in low brackets often prefer Roth.

Solo 401(k) vs. SEP-IRA

The SEP-IRA is another popular self-employed retirement account. Key differences:

• Solo 401(k) allows employee contributions + employer contributions; SEP-IRA only allows employer contributions (up to 25% of compensation, max $70,000)
• At lower income levels, Solo 401(k) wins because of the flat employee contribution
• SEP-IRA is simpler to administer; Solo 401(k) requires more paperwork once assets exceed $250,000
• Solo 401(k) offers loan provisions; SEP-IRA does not

How to Open a Solo 401(k)

1. 1Choose a provider: Fidelity, Vanguard, Charles Schwab, and TD Ameritrade all offer no-fee Solo 401(k)s with broad investment options
2. 2Apply online: Usually takes 10-20 minutes
3. 3Adopt the plan document before December 31 of the year you want contributions to count
4. 4Make contributions by your tax filing deadline (including extensions)

Additional Features

• Loans: You can borrow up to 50% of your vested balance (max $50,000) from your Solo 401(k)
• Mega backdoor Roth: Some Solo 401(k) plans allow after-tax contributions that can be converted to Roth, enabling massive Roth contributions beyond normal limits
• Investment flexibility: Most brokerages let you invest in stocks, ETFs, mutual funds, and bonds