Yes, 1099 workers can contribute to a solo 401(k). If your self-employment income comes from a business with no employees other than yourself (and possibly a spouse), you qualify to open what the IRS calls a one-participant 401(k) plan and contribute in two roles at once: as the worker deferring salary and as the business making a profit-sharing contribution.1Internal Revenue Service. One-Participant 401(k) Plans For 2026, the combined ceiling is $72,000, with additional room for those 50 and older.
Who Qualifies
The core requirement is self-employment income from a business that employs no one other than you and, if applicable, your spouse. Sole proprietorships, single-member LLCs, partnerships, and S-corporations all fit, as long as no other common-law employees are on the payroll working more than 1,000 hours per year. Hiring the occasional independent subcontractor does not disqualify you; putting a W-2 employee on payroll does.
Only earned income counts toward what you can contribute. For sole proprietors that means net profit on Schedule C; for partners, your share of partnership income on Schedule K-1. Passive income like rental payments and investment dividends is not part of the calculation.2Internal Revenue Service. Self-Employed Individuals – Calculating Your Own Retirement Plan Contribution and Deduction
The Two-Role Contribution Structure
The plan works because federal tax law lets you contribute as both the employee and the employer of your own business.1Internal Revenue Service. One-Participant 401(k) Plans Each role has its own limit, and they stack.
On the employee side, you can defer up to $24,500 of your earned income for 2026, or 100% of that income if it is less than the limit.3Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500 On the employer side, your business can add up to 25% of compensation as a profit-sharing contribution. For sole proprietors and single-member LLCs, the effective rate works out to roughly 20% of net self-employment income, because the contribution itself reduces the compensation base used in the calculation.2Internal Revenue Service. Self-Employed Individuals – Calculating Your Own Retirement Plan Contribution and Deduction
Net self-employment income for this purpose equals your Schedule C profit minus the deductible half of your self-employment tax. The self-employment tax rate is 15.3%: 12.4% for Social Security and 2.9% for Medicare.4Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes)
S-corporation owners calculate differently. Both the employee deferral and the 25% employer contribution are based on the W-2 salary the corporation pays you, not on shareholder distributions.
2026 Contribution Limits by Age
The combined employee-plus-employer contribution is capped at $72,000 for 2026 if you are under 50.5Internal Revenue Service. 2026 Amounts Relating to Retirement Plans and IRAs, as Adjusted for Changes in Cost-of-Living – Notice 2025-67 The maximum compensation that can be factored in is $360,000. Catch-up contributions then layer on top:
- Under 50: up to $24,500 in employee deferrals plus employer profit-sharing, capped at $72,000 combined.
- Ages 50 to 59, and 64 and older: an extra $8,000 catch-up brings the combined ceiling to $80,000.3Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
- Ages 60 through 63: a higher catch-up of $11,250 replaces the $8,000, bringing the ceiling to $83,250.3Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
Your practical maximum still depends on your net self-employment income. Earn $60,000 in profit and your ceiling is far below $72,000, no matter what the statutory cap says.
Traditional or Roth
Most solo 401(k) plans let you split employee deferrals between traditional (pre-tax) and Roth (after-tax) contributions. Traditional dollars come off your taxable income today and get taxed as ordinary income on withdrawal. Roth dollars are taxed now, and qualified withdrawals after age 59½ (once the account has been open at least five years) come out tax-free, including all earnings.6Internal Revenue Service. Roth Comparison Chart
Employer profit-sharing contributions were traditionally pre-tax only. SECURE 2.0 now allows them to be designated as Roth if the plan document permits and you elect that treatment. Not every custodian has updated its documents to offer this, so ask before assuming it is available.
One rule to know if you also have W-2 income: starting in 2026, if you received more than $150,000 in FICA wages from an employer in the prior year, any catch-up contributions to that employer’s plan must be made as Roth.5Internal Revenue Service. 2026 Amounts Relating to Retirement Plans and IRAs, as Adjusted for Changes in Cost-of-Living – Notice 2025-67
If You Also Have a W-2 Job
A lot of 1099 workers have a day job with its own 401(k). The trap: the $24,500 employee deferral limit is a per-person limit across all your 401(k) plans combined, not per plan.7Internal Revenue Service. How Much Salary Can You Defer if You’re Eligible for More Than One Retirement Plan Defer $20,000 into your employer’s plan, and you have $4,500 of deferral room left on the solo side.
The employer profit-sharing side has its own separate ceiling. Even if your employee deferrals are maxed at the W-2 job, your business can still contribute up to 25% of your net self-employment income as profit-sharing. The overall $72,000 per-employer limit under Section 415 applies separately to each unrelated employer’s plan.
Exceeding the combined deferral limit is expensive. The excess is taxed in the year you contributed it and taxed again when you eventually withdraw it.8Internal Revenue Service. Consequences to a Participant Who Makes Excess Deferrals to a 401(k) Plan You can avoid the double hit by requesting a corrective distribution of the excess by April 15 of the following year.
Deadlines to Set Up and Fund
You must formally adopt the plan by December 31 of the year you want to contribute for. Retroactive adoption after year-end is not allowed, even if you file for a tax extension.
Once the plan exists, deposit deadlines split by contribution type and business structure:
- Employee deferrals for sole proprietors and single-member LLCs: elect the deferral by December 31, but the deposit can be made until your tax filing deadline of April 15, or October 15 with an extension.
- Employee deferrals for S-corporations: deposit within a few days of the payroll date, following Department of Labor safe harbor guidelines.
- Employer profit-sharing contributions: due by your business tax filing deadline, including extensions.
Solo 401(k) vs. SEP IRA
The SEP IRA is the other common self-employed option, and the differences matter for a 1099 worker deciding where to save.
- A SEP IRA only allows employer contributions of up to 25% of compensation. There is no employee deferral, so at moderate income levels a solo 401(k) usually lets you save more.
- SEP IRAs do not permit catch-up contributions for those 50 and older. Solo 401(k) plans do.9Internal Revenue Service. SEP Contribution Limits (Including Grandfathered SARSEPs)
- SEP IRAs currently offer no Roth option. Solo 401(k) plans can include Roth on the employee side.
- Solo 401(k) plans can allow participant loans if the plan document permits; SEP IRAs cannot.
- A SEP IRA has no annual filing requirement at any balance. A solo 401(k) triggers a Form 5500-EZ filing once assets exceed $250,000.
How to Open a Solo 401(k)
Setup is administrative, not legal work. The plan needs its own Employer Identification Number, separate from any EIN your business already uses. Sole proprietors establishing a qualified retirement plan are specifically required to obtain one, and the online application on the IRS website issues the number immediately.10Internal Revenue Service. Form SS-4 – Application for Employer Identification Number
You then need a written plan document, often called a Plan Adoption Agreement, which establishes the trust that holds the retirement assets. Most brokerages and solo 401(k) providers supply a pre-approved template. You choose a plan name, an effective date on or before December 31, and your selections on features like Roth contributions, loans, and hardship withdrawals.
Submit the completed agreement with your legal name, address, Social Security number, and beneficiary designations to the custodian. After approval, transfer funds from your business bank account into the new plan account, and label each deposit as either an employee deferral or an employer profit-sharing contribution. The tax treatment and reporting are different, so the categorization matters.
Annual Reporting Once Assets Grow
Solo 401(k) plans with total assets above $250,000 at the end of the plan year must file Form 5500-EZ (or Form 5500-SF with the one-participant plan box checked) with the IRS.11Internal Revenue Service. Financial Advisors – Are Assets in Your Clients One-Participant Plans More Than $250,000 Plans below that threshold have no annual filing requirement unless the plan is being terminated.
The form is due by the last day of the seventh month after the plan year ends, which is July 31 for calendar-year plans, with a possible extension by filing Form 5558. Missing the deadline carries a penalty of $250 per day, up to $150,000 per plan year.12Internal Revenue Service. 2025 Instructions for Form 5500-EZ Put the date on the calendar the year your balance crosses the threshold.