Calculate your maximum Solo 401k contribution limits for 2024. Includes employee deferrals, employer profit sharing, and catch-up contributions.
Under 50: No catch-up allowed
~$11,933 estimated tax savings (25% bracket)
Solo 401k limits are per person, not per plan. If you participate in multiple 401k plans, your employee deferrals are combined across all plans.
A Solo 401k (also called Individual 401k, Self-Employed 401k, or One-Participant 401k) is a powerful retirement savings vehicle designed specifically for self-employed individuals and business owners who have no full-time employees other than themselves or a spouse. Among all retirement plans available to the self-employed, the Solo 401k offers the highest contribution limits combined with the most flexibility, making it an essential tool for building substantial retirement wealth.
The Solo 401k allows you to contribute in two capacities: as both an employee and an employer of your own business. This dual contribution structure is what enables such high annual contribution limits. As the employee, you can defer a portion of your earned income up to annual IRS limits. As the employer, you can make additional profit-sharing contributions based on your business compensation. When combined, these two contribution types allow self-employed individuals to shelter significantly more income from taxes compared to other retirement account options.
Unlike employer-sponsored 401k plans at large companies, the Solo 401k gives you complete control over your investment choices, plan administration, and contribution timing. You decide how much to contribute each year (within IRS limits), when to make those contributions, and how to invest the funds. This flexibility makes the Solo 401k particularly attractive for self-employed individuals whose income may fluctuate year to year.
The employee deferral component of a Solo 401k allows you to contribute a portion of your earned income on a pre-tax or Roth basis. For 2026, the employee deferral limit is $23,500 for individuals under age 50. Those who are 50 or older by the end of the calendar year can make an additional catch-up contribution of $7,500, bringing their total employee deferral to $31,000.
| Age | Base deferral limit | Catch-up contribution | Total employee deferral |
|---|---|---|---|
| Under 50 | $23,500 | $0 | $23,500 |
| 50 or older | $23,500 | $7,500 | $31,000 |
These deferral limits are aggregate limits that apply across all 401k plans in which you participate during the year. If you have a W-2 job with a 401k plan in addition to your self-employment income, your deferrals to both plans combined cannot exceed these limits. However, employer contributions from each plan are calculated separately based on compensation from that specific employer.
In addition to employee deferrals, Solo 401k participants can make employer profit-sharing contributions. The calculation method for these contributions depends on your business structure.
For corporations (including S-corporations and C-corporations), the employer can contribute up to 25% of the employee's W-2 wages. If you pay yourself a W-2 salary of $80,000 from your S-corporation, your maximum employer contribution would be $20,000 (25% × $80,000).
For sole proprietors, partnerships, and LLCs taxed as sole proprietorships, the calculation is more complex. The employer contribution is limited to 25% of "compensation," but compensation for sole proprietors is defined as net self-employment income minus half of the self-employment tax. This adjustment effectively reduces the contribution rate to approximately 20% of net self-employment income.
When combining employee deferrals and employer profit-sharing contributions, the total annual limit for 2026 is $70,000 for those under 50 and $77,500 for those 50 or older. These limits represent the maximum possible retirement savings available to self-employed individuals in a single year.
| Age | Employee deferral | Employer contribution | Maximum total |
|---|---|---|---|
| Under 50 | $23,500 | Up to $46,500 | $70,000 |
| 50 or older | $31,000 | Up to $46,500 | $77,500 |
Note that while the total limit is $70,000 (or $77,500), your actual maximum contribution depends on your compensation level. You cannot contribute more than your total business compensation for the year.
The contribution calculation for sole proprietors requires understanding several interconnected formulas. The process involves calculating self-employment tax, determining compensation, and then applying the contribution limits.
Step 1: Calculate self-employment tax
Self-employment tax applies to 92.35% of net self-employment income (this adjustment accounts for the employer-equivalent portion of FICA). The self-employment tax rate is 15.3% (12.4% for Social Security up to the wage base limit, plus 2.9% for Medicare).
Step 2: Determine compensation
For Solo 401k purposes, your compensation is your net self-employment income minus half of your self-employment tax. This mirrors how W-2 employees effectively have half their Social Security and Medicare taxes paid by their employer.
Step 3: Calculate maximum contributions
Detailed example: Sole proprietor, age 45, $100,000 net income
Detailed example: Sole proprietor, age 55, $150,000 net income
S-corporation owners have a simpler calculation because their compensation is based on their W-2 wages rather than self-employment income. The S-corp pays the employer portion of payroll taxes directly, so no SE tax adjustment is needed.
Detailed example: S-corp owner, age 52, $60,000 W-2 salary
Detailed example: S-corp owner, age 48, $120,000 W-2 salary
Many self-employed individuals wonder why they can only contribute approximately 20% of net self-employment income as an employer contribution rather than the stated 25%. The answer lies in the circular nature of the calculation.
When you make an employer contribution, that contribution reduces your net self-employment income. The IRS accounts for this by requiring you to first reduce your income by half the self-employment tax, which effectively yields a maximum employer contribution rate of about 20% of your original net income. The exact percentage varies slightly based on your income level due to the Social Security wage base limit.
The SEP IRA (Simplified Employee Pension) is another popular retirement plan for the self-employed. Understanding the differences helps you choose the right plan for your situation.
| Feature | Solo 401k | SEP IRA |
|---|---|---|
| 2026 maximum (under 50) | $70,000 | $70,000 |
| 2026 maximum (50+) | $77,500 | $70,000 |
| Employee deferrals | Yes ($23,500) | No |
| Catch-up contributions | Yes ($7,500) | No |
| Roth contribution option | Yes | No |
| Loan provision available | Yes (plan dependent) | No |
| Administrative complexity | Moderate | Very low |
| Form 5500-EZ required | When assets exceed $250,000 | Never |
| Contribution deadline | Tax filing deadline | Tax filing deadline |
| Plan establishment deadline | December 31 | Tax filing deadline |
When the Solo 401k is the better choice:
The Solo 401k excels for self-employed individuals with lower to moderate income levels. Because the Solo 401k includes an employee deferral component, you can contribute more at lower income levels than with a SEP IRA. For example, if you earn $50,000 in net self-employment income, a SEP IRA limits you to approximately $9,300 in contributions (20% of adjusted income), while a Solo 401k allows you to contribute approximately $32,500 (the full $23,500 employee deferral plus employer contribution).
The Solo 401k is also preferable when you want access to Roth contributions, need the ability to take loans from your retirement account, or are age 50 or older and want to take advantage of catch-up contributions.
When the SEP IRA is the better choice:
The SEP IRA shines when simplicity is paramount. There are no annual reporting requirements, plan establishment can occur up to the tax filing deadline (including extensions), and administration is minimal. For high earners who don't need Roth contributions or catch-up provisions, the SEP IRA provides similar maximum contributions with less administrative burden.
The SIMPLE IRA is designed for small businesses but can also be used by self-employed individuals. However, it has lower contribution limits: $16,500 in employee deferrals for 2026 (plus $3,500 catch-up if 50+) and a maximum employer match of 3% of compensation. The total maximum contribution is significantly lower than both the Solo 401k and SEP IRA, making it less attractive for self-employed individuals seeking to maximize retirement savings.
Individual Retirement Accounts (IRAs) have much lower contribution limits ($7,000 for 2026, or $8,000 if 50+) and Roth IRA contributions are subject to income phase-outs. The Solo 401k allows for significantly higher contributions and the Roth Solo 401k option has no income limits. However, IRAs can complement a Solo 401k as part of a comprehensive retirement strategy.
One of the most valuable features of the Solo 401k is the ability to make Roth (after-tax) contributions. Many Solo 401k plan documents allow participants to designate some or all of their employee deferrals as Roth contributions.
With Roth contributions, you pay income tax on the money now, but qualified withdrawals in retirement are completely tax-free—including all investment growth. This contrasts with traditional (pre-tax) contributions, where you get a tax deduction now but pay income tax on all withdrawals in retirement.
Key Roth Solo 401k rules:
Choosing between Roth and traditional contributions depends primarily on your current versus expected future tax rates.
| Factor | Favors traditional | Favors Roth |
|---|---|---|
| Current tax bracket | High | Low |
| Expected retirement bracket | Lower than current | Higher than current |
| Years until retirement | Fewer | Many |
| Tax diversification | Already have Roth savings | Mostly traditional savings |
| Estate planning | Less concern | Want tax-free inheritance |
General guidelines:
Solo 401k participants can also perform Roth conversions within the plan (if permitted by the plan document) or by rolling traditional Solo 401k funds to a Roth IRA. A Roth conversion involves paying income tax on the converted amount now in exchange for tax-free growth and withdrawals later. This strategy can be particularly valuable in years when your income is lower than usual.
To establish a Solo 401k, you must meet specific criteria:
Required:
Business types eligible:
You can establish a Solo 401k for a side business even if you have a W-2 job with another employer. However, your employee deferral limits are aggregate across all 401k plans.
Solo 401k plans are available from various providers with different features and costs.
Free brokerage plans:
Major brokerages like Fidelity, Charles Schwab, and Vanguard offer free Solo 401k plans with no setup fees, annual fees, or transaction costs beyond standard trading commissions. These plans typically offer:
Full-featured plans:
For maximum flexibility, providers like Etrade, Rocket Dollar, and specialized Solo 401k administrators offer plans with additional features:
Plan establishment: Your Solo 401k plan must be established by December 31 of the tax year for which you want to make contributions. This means signing plan documents and setting up the account by year-end. You cannot retroactively establish a plan after year-end.
Employee deferrals: Employee deferral contributions must be made by December 31 of the tax year. Unlike employer contributions, you cannot make deferrals after year-end. For sole proprietors, this deadline is somewhat flexible since you are both the employer and employee, but best practice is to make deferrals by December 31.
Employer contributions: Employer profit-sharing contributions can be made up to your tax filing deadline, including extensions. For calendar-year filers, this is typically April 15, or October 15 with an extension. This provides significant flexibility in determining your final contribution amount after knowing your actual business income.
Every Solo 401k must have a written plan document that specifies the plan's terms, including:
Most providers supply pre-approved plan documents. Some providers offer IRS opinion letter plans, which have been pre-reviewed by the IRS for compliance. Using a provider's standard plan document is typically sufficient for most Solo 401k participants.
Traditional Solo 401k contributions reduce your taxable income dollar-for-dollar. The tax savings depend on your marginal tax bracket.
| Contribution amount | Tax savings (22% bracket) | Tax savings (32% bracket) | Tax savings (37% bracket) |
|---|---|---|---|
| $23,500 | $5,170 | $7,520 | $8,695 |
| $47,000 | $10,340 | $15,040 | $17,390 |
| $70,000 | $15,400 | $22,400 | $25,900 |
In addition to federal tax savings, Solo 401k contributions reduce your state income tax liability in most states. California taxpayers in the 9.3% bracket save an additional $6,510 on a $70,000 contribution. Combined federal and state tax savings can exceed 45% of the contribution amount in high-tax states.
Solo 401k contributions do not directly reduce self-employment tax (unlike some other deductions). However, the retirement savings still provide significant tax advantages through the income tax deduction and tax-deferred growth.
The true power of tax-advantaged retirement accounts lies in compound growth over time. By deferring taxes on investment gains, your money grows faster than it would in a taxable account.
Example: $50,000 annual contribution at 7% average return
| Years of contributions | Solo 401k value | After-tax account value (assuming 15% capital gains) |
|---|---|---|
| 10 | $691,000 | $623,000 |
| 15 | $1,257,000 | $1,106,000 |
| 20 | $2,049,000 | $1,767,000 |
| 25 | $3,166,000 | $2,674,000 |
The Solo 401k provides an additional $492,000 after 25 years in this example, purely from tax-deferred compounding.
The most critical deadline is December 31 for plan establishment. Unlike a SEP IRA (which can be established up to the tax filing deadline), a Solo 401k must exist by year-end. Many self-employed individuals miss this deadline and lose an entire year of potential contributions.
Sole proprietors frequently make errors by using gross self-employment income rather than the adjusted compensation figure. Remember: you must subtract half of your self-employment tax from net self-employment income to determine your compensation for Solo 401k purposes.
If you participate in multiple 401k plans (for example, a W-2 job plus self-employment), your total employee deferrals across all plans cannot exceed $23,500 ($31,000 if 50+). Exceeding this limit results in penalties and required corrective distributions.
Solo 401k plans with assets exceeding $250,000 at year-end must file Form 5500-EZ annually with the IRS. The form is due by the last day of the seventh month after the plan year ends (July 31 for calendar-year plans). Failure to file can result in penalties of $250 per day, up to $150,000.
Your total Solo 401k contributions cannot exceed your compensation from the business sponsoring the plan. If your self-employment income is $30,000, your maximum contribution is limited by that amount, regardless of the higher IRS limits.
If you hire full-time employees (working 1,000+ hours per year), you may no longer be eligible for a Solo 401k. You would need to convert to a standard 401k plan that covers all eligible employees, which involves significant additional cost and complexity.
If your spouse works in your business and receives reasonable compensation, they can also participate in the Solo 401k with their own contributions:
This effectively doubles your household's retirement savings potential. A couple where both spouses are 50+ could potentially contribute up to $155,000 annually.
Example: Married couple, both age 55, business earns $200,000
Assuming $100,000 compensation allocated to each spouse:
Compensation paid to a spouse must be reasonable for the work performed. The IRS may challenge excessive compensation designed primarily to inflate retirement contributions. Document your spouse's work hours and responsibilities to support the compensation level.
Most Solo 401k participants invest in traditional securities available through their brokerage:
Self-directed Solo 401k plans allow investment in alternative assets:
Self-directed plans require a specialized custodian and involve additional complexity, fees, and compliance requirements. Prohibited transaction rules must be carefully followed—you cannot use Solo 401k funds to purchase property you personally use or to transact with certain family members.
Your Solo 401k asset allocation should consider:
Beginning at age 73 (increasing to 75 in 2033), Solo 401k participants must take required minimum distributions (RMDs) from traditional (pre-tax) account balances. RMDs are calculated based on your account balance and life expectancy factors.
Key RMD rules:
You can roll funds from other qualified retirement plans into your Solo 401k (if your plan document permits incoming rollovers):
Rolling old retirement accounts into your Solo 401k simplifies account management and may provide better investment options.
When you close your Solo 401k (for example, if you return to full-time employment), you can roll the balance to:
The Solo 401k represents the most powerful retirement savings tool available to self-employed individuals without employees. Its combination of high contribution limits, contribution flexibility, Roth option, and potential loan access makes it superior to other self-employed retirement plans in most situations.
Essential points to remember:
For self-employed individuals serious about building retirement wealth, the Solo 401k should be a cornerstone of their financial strategy. The ability to contribute over $70,000 annually with tax advantages provides an unmatched opportunity to accumulate significant retirement savings.