For 2026, a Solo 401(k) participant can generally defer up to $24,500 as an employee and may also make an employer contribution, subject to earned income and the plan’s terms. Total annual additions are generally capped at $72,000 before catch-up contributions.
Those published limits are ceilings, not automatic contribution amounts. A self-employed person’s actual Solo 401(k) contribution depends on earned income, age, other retirement-plan deferrals, business structure, and whether the business has employees.
Quick Answer
For 2026:
- Employee elective-deferral limit: $24,500
- Overall Section 415(c) annual-additions limit: $72,000 before catch-up contributions
- Standard catch-up contribution: $8,000 for eligible participants age 50 or older who are not in the special age-60-to-63 group
- Enhanced catch-up contribution: $11,250 for eligible participants who turn 60, 61, 62, or 63 during 2026, instead of the standard $8,000 catch-up
- 2026 compensation limit: $360,000
A Solo 401(k) owner contributes in two roles: as an employee through elective deferrals and as an employer through employer contributions. For a sole proprietor, the employer portion requires a special self-employed calculation — it is not simply 25% of Schedule C profit.
2026 Solo 401(k) Contribution Limits at a Glance
| Contribution Rule | 2026 Limit |
|---|---|
| Employee elective deferral | $24,500 |
| Standard catch-up contribution | $8,000 |
| Enhanced catch-up for ages 60–63 | $11,250 instead of $8,000 |
| Overall Section 415(c) annual-additions limit | $72,000 before catch-up |
| Potential total with standard catch-up | $80,000, if all requirements are satisfied |
| Potential total with enhanced catch-up | $83,250, if all requirements are satisfied |
| Annual compensation limit | $360,000 |
The IRS adjusts many of these limits for inflation. The figures above apply specifically to 2026.
How a Solo 401(k) Lets You Contribute in Two Roles
The IRS describes a one-participant 401(k) owner as wearing two hats: employee and employer.
Employee Elective Deferral
As the employee, the owner can generally make elective deferrals up to 100% of compensation — called earned income for a self-employed individual — subject to the annual elective-deferral limit.
For 2026, that dollar limit is $24,500 before catch-up contributions.
The plan may permit traditional pre-tax deferrals, Roth deferrals, or both. Roth availability depends on the plan document.
Employer Contribution
As the employer, the business can also make an employer nonelective contribution.
For a common-law employee, the plan formula can generally provide an employer contribution of up to 25% of compensation, subject to the plan and annual limits. A self-employed owner must use a special calculation because the owner’s earned income is reduced by the deductible portion of self-employment tax and by the contribution for the owner.
The IRS directs self-employed taxpayers to the rate table and worksheets in Publication 560 to calculate the allowable contribution.
How Much Can a Sole Proprietor Contribute?
A simplified conceptual calculation looks like this:
- Start with Schedule C net profit.
- Calculate self-employment tax.
- Determine the deductible portion of self-employment tax used in the retirement-plan calculation.
- Determine adjusted net earnings from self-employment.
- Apply the reduced employer contribution rate.
- Add the available employee elective deferral.
- Apply the annual deferral and annual-additions limits.
For a plan with a stated 25% employer contribution rate, the IRS Publication 560 rate table gives a 20% reduced contribution rate for the self-employed owner’s calculation.
For more background, see Schedule C Explained: How Freelancers Report Business Income and Expenses and How to Calculate Self-Employment Tax in 2026.
Why You Can’t Just Multiply Schedule C Profit by 25%
For a sole proprietor, saying “I can contribute 25% of my Schedule C profit” skips important parts of the IRS calculation.
First, the retirement-plan earned-income calculation takes into account the deductible portion of self-employment tax. Second, because the contribution itself affects the self-employed owner’s earned income, the stated plan contribution rate must be converted using the IRS rate table.
For a plan contribution rate of 25%, Publication 560 gives a reduced rate of 0.20, or 20%.
That 20% is applied to the relevant adjusted self-employment earnings — not directly to unadjusted Schedule C profit.
Example 1: $40,000 of Schedule C Net Profit
Assume:
- The owner is under age 50
- There are no employees
- There is no other retirement plan
- There are no W-2 wages
- The standard self-employment tax calculation applies
- The plan uses the standard 25% employer contribution formula, producing a 20% reduced self-employed rate
| Step | Approximate Amount |
|---|---|
| Schedule C net profit | $40,000 |
| Self-employment tax | $5,651.82 |
| One-half of SE tax | $2,825.91 |
| Adjusted amount used for this simplified employer-contribution calculation | $37,174.09 |
| Employer contribution at 20% | $7,434.82 |
| Employee elective deferral | $24,500 |
| Potential total contribution | $31,934.82 |
At this income level, the employee elective deferral creates most of the contribution capacity.
Example 2: $80,000 of Schedule C Net Profit
Using the same assumptions:
| Step | Approximate Amount |
|---|---|
| Schedule C net profit | $80,000 |
| Self-employment tax | $11,303.64 |
| One-half of SE tax | $5,651.82 |
| Adjusted amount used for this simplified employer-contribution calculation | $74,348.18 |
| Employer contribution at 20% | $14,869.64 |
| Employee elective deferral | $24,500 |
| Potential total contribution | $39,369.64 |
For a comparison with a SEP IRA at this income level, see Solo 401(k) vs SEP IRA: Which Is Better for Self-Employed Workers?.
Example 3: $150,000 of Schedule C Net Profit
Using the same assumptions:
| Step | Approximate Amount |
|---|---|
| Schedule C net profit | $150,000 |
| Self-employment tax | $21,194.33 |
| One-half of SE tax | $10,597.16 |
| Adjusted amount used for this simplified employer-contribution calculation | $139,402.84 |
| Employer contribution at 20% | $27,880.57 |
| Employee elective deferral | $24,500 |
| Potential total contribution | $52,380.57 |
Even with $150,000 of Schedule C profit, this example remains below the $72,000 annual-additions ceiling.
How Much Income Do You Need to Max Out a Solo 401(k)?
There is no universal income number, because business structure, other wages, other retirement plans, plan terms, and age can change the calculation.
Under the assumptions used above — sole proprietor, under age 50, no other wages, no other retirement plan, no employees, and the standard 25% employer formula — the owner needs a $47,500 employer contribution to combine with the $24,500 employee deferral and reach the $72,000 annual-additions ceiling.
Because the Social Security portion of self-employment tax stops increasing after the annual Social Security wage base is reached, the math is not perfectly linear at higher income.
Using the 2026 Social Security taxable maximum of $184,500, the approximate Schedule C net profit needed under these assumptions is about $252,300.
This is an estimate for one specific fact pattern, not a universal threshold.
Catch-up eligibility does not necessarily require more business profit to reach the higher total limit. Catch-up contributions sit on top of the $72,000 Section 415(c) limit. If the owner already has enough earned income to support the regular $72,000 annual additions and the catch-up contribution, the same underlying employer-contribution requirement can support a total of $80,000 or $83,250, depending on the applicable catch-up amount.
Catch-Up Contributions in 2026
Age 50 and Older
If the plan permits catch-up contributions, an eligible participant age 50 or older can generally make an additional $8,000 catch-up contribution in 2026, unless the enhanced age-60-to-63 limit applies.
Ages 60–63
A participant who turns 60, 61, 62, or 63 during 2026 can generally make an enhanced catch-up contribution of $11,250 instead of the standard $8,000 amount.
Catch-up contributions are not counted inside the regular $72,000 Section 415(c) annual-additions limit.
Mandatory Roth Catch-Up Rule for 2026
Beginning in 2026, certain higher-wage participants must make catch-up contributions on a Roth basis.
For 2026, the relevant prior-year wage threshold is $150,000. The IRS rule looks to prior-year FICA wages from the employer sponsoring the plan.
This distinction matters for a purely self-employed sole proprietor. The final IRS regulations explain that an individual with no prior-year FICA wages from the sponsoring employer — for example, someone whose income from that employer consisted only of self-employment income — is not subject to the Roth catch-up requirement under that plan on that basis.
W-2 wages from an unrelated employer do not automatically become wages from the Solo 401(k)’s sponsoring business for this test. More complicated ownership or employer-aggregation arrangements can require a closer review.
The plan must also support Roth contributions for the Roth catch-up rules to operate as required.
What If You Also Have a W-2 401(k)?
The employee elective-deferral limit is generally by person, not by plan.
If you defer $15,000 into a workplace 401(k) in 2026, you generally have only:
$24,500 − $15,000 = $9,500
of the standard employee elective-deferral limit remaining for a Solo 401(k).
Deferrals to a 403(b) generally coordinate with the same personal elective-deferral limit. Governmental 457(b) plans operate under a separate statutory deferral limit.
Employer Contributions Can Be Different
The Section 415(c) annual-additions limit can apply separately to plans maintained by unrelated employers. The IRS gives an example in which a business owner who used the full personal elective-deferral limit at another employer could still make a substantial employer nonelective contribution to a Solo 401(k) maintained by an unrelated self-employed business.
That separate treatment should not be assumed when businesses are related through common ownership or other aggregation rules.
Traditional vs Roth Solo 401(k) Contributions
Traditional elective deferrals generally reduce current federal taxable income, subject to the tax and plan rules.
Roth elective deferrals are included in current taxable income and do not provide the same current-year income-tax reduction. Qualified Roth distributions can generally be tax-free when the applicable requirements are satisfied.
SECURE 2.0 also permits certain employer matching and nonelective contributions to be designated as Roth if the plan supports the feature and the statutory requirements are satisfied.
Whether traditional or Roth treatment is preferable depends on the taxpayer’s circumstances and is not determined by the contribution limit alone.
Do Solo 401(k) Contributions Reduce Self-Employment Tax?
Generally, no.
Solo 401(k) contributions are not deducted as Schedule C business expenses and therefore do not reduce Schedule C net profit.
The self-employment tax calculation is made without subtracting the Solo 401(k) contribution from Schedule C profit. Traditional retirement-plan contributions can affect federal taxable income elsewhere on the return, but that is separate from the self-employment tax calculation.
Roth elective deferrals do not provide the same current-year federal income-tax reduction as traditional elective deferrals.
Contribution Deadlines for a Sole Proprietor
Deadlines are one of the easiest parts of Solo 401(k) rules to oversimplify.
Existing Plan: Employee Elective Deferral
For an owner-employee, IRS Publication 560 states that elective deferrals generally must be elected by the end of the tax year. The contribution can then generally be deposited by the tax-return filing deadline, including extensions.
Employer Contribution
Employer profit-sharing or nonelective contributions can generally be made after year-end and still be deductible for the prior tax year when they are made by the applicable tax-return due date, including extensions, and the other requirements are satisfied.
Special First-Year Rule for a New Sole-Proprietor 401(k)
SECURE 2.0 created a special rule for the first year of a new plan. An individual who owns an entire unincorporated business and is the only employee can adopt a new 401(k) after year-end and, for the first year only, make the prior-year elective-deferral election as late as the due date of the individual’s tax return without extensions.
This special rule should not be confused with the ordinary deadline for an already-existing plan.
Solo 401(k) Limits for Different Business Structures
Sole Proprietor
A sole proprietor generally uses the special self-employed earned-income calculation, including the reduced contribution-rate method described above.
Single-Member LLC
A single-member LLC’s retirement-plan calculation depends on its federal tax classification. A disregarded single-member LLC owned by an individual generally follows the sole-proprietor approach. An LLC that elected corporate tax treatment follows the rules applicable to that corporate structure.
S Corporation Owner
An S corporation owner’s retirement-plan contributions are generally based on eligible W-2 compensation as defined under the plan, not shareholder distributions.
The sole-proprietor self-employment calculation therefore does not apply in the same way. An S corporation owner should not use shareholder distributions as though they were compensation for Solo 401(k) contribution purposes.
What Happens If You Hire Employees?
A one-participant 401(k) receives its simplified treatment because it covers only the business owner, or the owner and spouse.
If the business hires common-law employees who satisfy the plan’s eligibility requirements, those eligible employees generally must be included. The plan then becomes subject to the rules that apply to an ordinary employee 401(k), including nondiscrimination testing unless an applicable exception such as a safe-harbor design applies.
That does not automatically mean the legal plan must be terminated and replaced, but the owner-only treatment disappears and the plan must be operated accordingly.
Form 5500-EZ
A one-participant 401(k) is not paperwork-free forever.
Under the IRS filing rules, Form 5500-EZ generally is not required when the combined year-end assets of all one-participant plans maintained by the employer are $250,000 or less, unless it is the plan’s final year.
When combined assets exceed $250,000, the annual filing requirement generally applies. A final return is required for the final plan year regardless of the asset amount.
For a calendar-year plan, the normal deadline is the last day of the seventh month after year-end — generally July 31.
Form 5500-EZ can be filed electronically through EFAST2. Some filers are required to file electronically under the IRS’s broader electronic-filing rules; otherwise paper filing may remain available under the applicable instructions.
What Happens If You Contribute Too Much?
An excess contribution or excess elective deferral should be addressed promptly. The correct procedure depends on which limit was exceeded, the contribution type, when the error was discovered, and the plan’s terms.
Because different correction rules and deadlines can apply, a participant who discovers an excess should contact the plan provider or a qualified retirement-plan or tax professional rather than improvising a correction.
Common Solo 401(k) Contribution Mistakes
- Applying 25% directly to Schedule C profit.
- Ignoring the special self-employed earned-income calculation.
- Forgetting the personal elective-deferral limit across multiple 401(k) and 403(b) plans.
- Assuming every self-employed person can contribute $72,000.
- Assuming catch-up contributions count inside the $72,000 limit.
- Assuming catch-up eligibility means more business profit is always needed to reach the higher total ceiling.
- Using shareholder distributions instead of eligible W-2 compensation for an S corporation owner.
- Assuming Solo 401(k) contributions reduce self-employment tax.
- Using the first-year sole-proprietor deadline for an already-existing plan.
- Forgetting Form 5500-EZ once combined one-participant plan assets exceed $250,000.
- Ignoring eligible employees.
Solo 401(k) Contribution Checklist
- Calculate business profit or eligible compensation for the correct business structure.
- For a sole proprietor, calculate self-employment tax and the applicable earned-income adjustment.
- Use the IRS self-employed contribution rate table or worksheet.
- Determine how much of the $24,500 personal elective-deferral limit remains after other plans.
- Check catch-up eligibility.
- Confirm whether the plan permits Roth contributions.
- Check the $72,000 annual-additions limit.
- Confirm the correct election and deposit deadlines.
- Review whether the business has eligible employees.
- Track combined one-participant plan assets for Form 5500-EZ purposes.
Frequently Asked Questions
What is the Solo 401(k) contribution limit for 2026?
The standard employee elective-deferral limit is $24,500. The overall annual-additions limit is generally $72,000 before catch-up contributions, subject to compensation, earned-income, plan, and other statutory limits.
Can I automatically contribute the full $72,000?
No. Your earned income or compensation must be sufficient to support the employee and employer contributions, and other retirement-plan contributions can affect the amount available.
How much can I contribute with $50,000 of Schedule C net profit?
Under the same simplified assumptions used in the examples above — under age 50, no other retirement plan, no employees, no other wages, and the standard self-employment tax calculation — the estimated employer contribution is about $9,293.52. Adding a $24,500 employee elective deferral produces a potential total of about $33,793.52.
Can I contribute 25% of Schedule C profit?
Not directly. A self-employed owner must use the special IRS earned-income calculation. Under a plan with a stated 25% contribution rate, the Publication 560 rate table gives a 20% reduced rate for the self-employed calculation.
Can I have a Solo 401(k) and a workplace 401(k)?
Yes. However, the personal elective-deferral limit is generally shared across 401(k) plans, so contributions to the workplace plan reduce the employee-deferral room available in the Solo 401(k).
Do Solo 401(k) contributions reduce self-employment tax?
Generally no. They do not reduce Schedule C net profit and therefore do not directly reduce the self-employment tax calculation.
Can I make Roth Solo 401(k) contributions?
Yes, if the plan document supports designated Roth contributions. Not every provider or plan document offers every Roth feature.
What is the catch-up limit for 2026?
The standard catch-up limit is $8,000. For participants who turn 60, 61, 62, or 63 during 2026, the enhanced catch-up is $11,250 instead of $8,000.
What happens if I hire an employee?
If a common-law employee becomes eligible under the plan, the employee generally must be included. The plan can no longer rely on the simplified one-participant treatment.
Do I need Form 5500-EZ?
Generally, a one-participant plan is exempt while the combined assets of the employer’s one-participant plans are $250,000 or less at year-end, unless it is the final plan year. Once the combined assets exceed $250,000, annual filing generally becomes required.
Bottom Line
The 2026 Solo 401(k) limits — $24,500 for the standard employee elective deferral and $72,000 for annual additions before catch-up — are maximum ceilings, not automatic contribution amounts.
For a self-employed owner, the actual number depends on earned income, business structure, age, other retirement plans, employees, and the special IRS contribution calculation.
The biggest practical mistake is using a simple “25% of Schedule C profit” shortcut. For a sole proprietor, use the IRS self-employed contribution worksheets or reliable tax software before making a maximum contribution.
This article is for general educational purposes and is not individualized tax, legal, retirement-plan, or investment advice. Retirement-plan rules can change, and actual contribution limits depend on individual facts and plan terms.
Official Sources
- IRS — One-Participant 401(k) Plans
- IRS — 2026 Cost-of-Living Adjusted Retirement Plan Limits
- IRS — 401(k) Limit Increases to $24,500 for 2026
- IRS — Publication 560, Retirement Plans for Small Business
- IRS — Catch-Up Contributions
- IRS — Final Regulations on the Roth Catch-Up Requirement
- IRS — 401(k) Contribution and Retroactive Adoption Timing
- IRS — Form 5500-EZ Filing Requirements
- IRS — About Form 5500-EZ