The Solo 401(k) offers one of the highest contribution ceilings available to self-employed individuals. In 2026, a qualifying participant can contribute up to $72,000 to the plan, or $83,250 with the catch-up available to ages 60 through 63. What makes that possible is a dual-contribution structure found in no other self-directed plan type: you contribute once as the employee of your business, and again as the employer.
This page explains how each contribution type works, how the limits are calculated based on business structure, age-based catch-up provisions, and contribution deadlines. Because your specific allowable amount depends on net business income, business entity type, and other retirement plan participation, we encourage you to work with a qualified tax advisor on contribution strategy. The limits below define the ceiling; your advisor helps you determine the optimal amount for your situation.
2026 Solo 401(k) contribution limits
Source: IRS Notice 2025-67 | Effective for the 2026 tax year
| Contribution Type | 2026 Limit |
|---|---|
| Employee Salary Deferral | $24,500 |
| Employer Profit-Sharing (W-2 wages) | Up to 25% of W-2 wages |
| Employer Profit-Sharing (Self-employed) | Up to 20% of net self-employment income |
| Catch-Up (Age 50-59 or Age 64+) | $8,000 |
| Super Catch-Up (Age 60-63) | $11,250 |
| Plan Maximum (Under age 50) | $72,000 |
| Plan Maximum (Age 50-59 or Age 64+) | $80,000 |
| Plan Maximum (Age 60-63) | $83,250 |
Maximum compensation considered for calculations: $360,000 (IRC §401(a)(17))
How the two contribution types work together
The Solo 401(k)'s contribution power comes from stacking two legally distinct contribution sources.
Employee salary deferrals operate exactly like a traditional 401(k) at any employer. You defer a portion of your compensation into the plan, pre-tax or Roth, up to the annual employee limit. This amount is shared across all 401(k)-type plans you participate in during the year; it is not per-plan.
Employer profit-sharing contributions are made by the business itself. They may be designated as Traditional (pre-tax) or Roth, calculated as a percentage of qualifying compensation, and carry their own limit separate from employee deferrals. They do not reduce your employee deferral capacity, and your employee deferral does not reduce what the business can contribute; the two work in parallel.
Combining these sources is how eligible participants reach the plan maximum. A self-employed consultant earning $200,000 in net business income, for example, could contribute $24,500 as the employee and add an employer contribution up to 20% of net self-employment income, working toward the $72,000 plan ceiling.
Employer profit-sharing: the calculation differs by business structure
How you pay yourself determines how the employer contribution is calculated.
S-corporation or C-corporation (W-2 wages): The employer contribution can be up to 25% of your W-2 wages. Shareholder distributions do not count for this purpose; only W-2 compensation is included in the base.
Sole proprietorship or single-member LLC (pass-through / self-employed): The calculation uses net self-employment income after deducting half of self-employment taxes. Because the employer contribution itself reduces the base before the percentage is applied, the effective contribution rate works out to approximately 20% of net profit after the SE tax deduction. IRS Publication 560 contains the specific worksheet for this calculation.
In either structure, the employer contribution is capped at the lesser of the applicable percentage or the plan maximum remaining after any employee deferrals.
Catch-up contributions: age 50 and beyond
Participants who turn 50 or older during the calendar year can make additional employee deferrals beyond the standard limit.
In 2026, the standard catch-up is $8,000, raising total employee deferral capacity to $32,500 and the plan maximum to $80,000 for participants ages 50 through 59 and 64 and older.
SECURE 2.0 Act created an enhanced "super catch-up" for participants who turn 60, 61, 62, or 63 during the tax year. These participants contribute $11,250 as their catch-up rather than $8,000, raising total employee deferral capacity to $35,750 and the plan maximum to $83,250. At age 64, participants return to the standard $8,000 catch-up.
Important: Participants with prior-year FICA wages exceeding $150,000 are required under IRC §414(v)(7)(A) to designate all catch-up contributions as Roth contributions in 2026. Pre-tax catch-up contributions are not available to participants above this wage threshold. Regular salary deferrals remain your choice of Traditional or Roth regardless of income.
A fourth contribution type: nondeductible
The Solo 401(k) supports a fourth contribution type: nondeductible (after-tax) employee contributions. These are not subject to the standard deferral limit and can be used to fill the gap between your compensation-based allowable contributions and the plan maximum.
Nondeductible contributions are not tax-deductible, but earnings grow tax-deferred. Their real value lies in the Mega Backdoor Roth strategy, where after-tax contributions are converted to Roth inside the plan, allowing for tax-free growth.
Not all Solo 401(k) plan documents support this feature. Self-Directed Plans Solo 401(k)s do.
Contribution deadlines
Deadlines vary by contribution type and business structure. SECURE 2.0 significantly expanded flexibility for self-employed filers, including the ability to both establish and fund a plan after December 31.
| Contribution Type | Deadline |
|---|---|
| Plan establishment | Tax filing deadline, including extensions |
| Employee deferral (sole proprietor or pass-through) | Tax filing deadline, including extensions |
| Employee deferral (W-2 / corporate environment) | December 31 of the plan year |
| Employer profit-sharing | Tax filing deadline, including extensions |
For most sole proprietors and single-member LLCs, the extended deadline runs through October 15 of the following calendar year. This applies to both plan establishment and contributions: a Solo 401(k) opened in September 2027 can still accept 2026 employee deferrals and employer contributions, provided the business files an extension.
The W-2 exception is meaningful: if your business pays you through payroll, employee deferrals must be withheld and deposited before December 31. W-2 wages cannot be reduced retroactively, so the deferral opportunity closes with the calendar year even if the plan itself could technically be established later.
2025 contribution limits: prior year reference
Contributions attributable to the 2025 tax year may still be made through the business filing deadline, including extensions, generally October 15, 2026 for sole proprietors and pass-through entities. Source: IRS Notice 2024-80.
| Contribution Type | 2025 Limit |
|---|---|
| Employee Salary Deferral | $23,500 |
| Employer Profit-Sharing (W-2 wages) | Up to 25% of W-2 wages |
| Employer Profit-Sharing (Self-employed) | Up to 20% of net self-employment income |
| Catch-Up (Age 50-59 or Age 64+) | $7,500 |
| Super Catch-Up (Age 60-63) | $11,250 |
| Plan Maximum (Under age 50) | $70,000 |
| Plan Maximum (Age 50-59 or Age 64+) | $77,500 |
| Plan Maximum (Age 60-63) | $81,250 |
Maximum compensation considered for calculations: $350,000 (IRC §401(a)(17))
Contribution limits vs. contribution strategy
The limits on this page define what the IRS permits. They do not define what is right for your situation.
Contribution strategy, how much to contribute, whether to elect Traditional or Roth treatment, and how to sequence contributions across a year of variable income, depends on your tax position, income projections, and broader financial picture. For guidance on optimizing contributions for your specific circumstances, consult a CPA or tax professional with experience in self-employment retirement planning.
IRS Publication 560 (Retirement Plans for Small Business) is the primary reference for contribution calculations and is updated annually.
Disclosure
This information is provided for educational purposes only and should not be interpreted as tax, legal, or investment advice. Readers are encouraged to consult a qualified professional who can offer guidance based on their personal situation.