Short answer: A solo 401(k) (also called a self-employed or one-participant 401(k)) lets a business owner with no employees save as both employee and employer. For 2026 you can defer up to $24,500 of your own income, add a profit-sharing contribution of up to about 20% of your net self-employment earnings, and reach a combined limit of $72,000 ($80,000 at 50 or older, more at 60 to 63). Fidelity offers a self-employed 401(k) with no setup or recurring maintenance fee reported, and you can often open it online. Check Fidelity’s current plan documents before you apply, because forms and features change.
Who Can Open a Solo 401(k) at Fidelity
- You are self-employed or own a business or partnership with no employees other than yourself and your spouse.
- You have earned income from that business. Investment income and rental income generally do not count.
- To open the plan entirely online, Fidelity has required you to be the plan administrator and participant, a U.S. citizen, and (if married) to name your spouse as primary beneficiary. Otherwise you use paper forms: an adoption agreement, a trust agreement and an account application.
- If you later hire a common-law employee who must be covered, the plan usually has to change. Talk to a tax professional before you hire.
2026 Solo 401(k) Contribution Limits (and the 2027 Outlook)
| Limit | 2026 (official) | 2027 (projected, not official) |
|---|---|---|
| Employee deferral (pre-tax or Roth) | $24,500 | $25,500 |
| Catch-up, age 50 or older | $8,000 | $8,500 |
| Catch-up, ages 60 to 63 | $11,250 | $11,750 |
| Total employee plus employer, before catch-up | $72,000 | $75,000 |
| Total with age 50+ catch-up | $80,000 | $83,500 |
| Pay the plan can count | $360,000 | $375,000 |
2026 figures are from IRS Notice 2025-67 and Fidelity’s learning center. 2027 figures are projections until the IRS announces them, usually in mid-November. See our Fidelity 401(k) contribution limits guide for the full table.
Your employee deferral limit is per person, not per plan. If you also have a 401(k) at a day job, your deferrals to both plans count toward the same $24,500.
How Much Can You Put In? Worked Examples
As the employer, a self-employed owner’s contribution is generally capped at 20% of net self-employment earnings after subtracting half of self-employment tax, rather than the 25% that applies to W-2 pay. Here is the math for a sole proprietor under 50 in 2026, using the IRS formula (net profit, minus half of self-employment tax, times 20% for the employer share) and a full $24,500 employee deferral.
| Net business profit | Half of self-employment tax | Employer contribution (20%) | Employee deferral | Total contribution |
|---|---|---|---|---|
| $40,000 | $2,826 | $7,435 | $24,500 | $31,935 |
| $60,000 | $4,239 | $11,152 | $24,500 | $35,652 |
| $100,000 | $7,065 | $18,587 | $24,500 | $43,087 |
| $150,000 | $10,597 | $27,881 | $24,500 | $52,381 |
These assume a sole proprietorship or single-member LLC taxed as one, no other income, and earnings below the Social Security wage base. The $100,000 row matches the example in Fidelity’s own guide. S corporation owners calculate differently, using W-2 salary. This is an illustration, not tax advice: use IRS Publication 560 or a tax professional for your return.
Solo 401(k) vs. SEP-IRA
| Solo 401(k) | SEP-IRA | |
|---|---|---|
| Employee deferrals | Yes, up to $24,500 in 2026 | No, employer contributions only |
| Employer contribution | Up to about 20% of net earnings (self-employed) | Up to about 20% of net earnings (self-employed) |
| Top total limit (2026) | $72,000, plus catch-up | $72,000, no catch-up |
| Best for | Lower or moderate income that wants to save a lot | Simplicity; higher income that already maxes the percentage |
| Paperwork | Plan documents; Form 5500-EZ above $250,000 in assets | Minimal |
At lower profits, the solo 401(k) usually lets you save more because the employee deferral does not depend on the percentage formula. At very high profits, both reach the same $72,000 ceiling.
Roth, Loans and Other Features to Confirm
- Roth: The tax rules let a solo 401(k) accept Roth employee deferrals. Whether a specific provider’s plan offers them depends on its plan documents. Check Fidelity’s adoption agreement before you apply.
- Loans: Solo 401(k) plans can allow loans under the same IRS limits as other 401(k)s (see our 401(k) loan guide), but not every provider’s plan does. Confirm in the documents.
- After-tax contributions and the “mega backdoor Roth”: These need plan features that vary by provider. Do not plan around them until you have confirmed they are allowed.
- Rollovers in: Some solo plans accept rollovers from old 401(k)s, which can matter if you want to avoid the IRA pro-rata rule. See our rollover guide.
Fees
Fidelity has been reported to charge no setup or recurring maintenance fee for its self-employed 401(k), with no commissions on stock and ETF trades and no transaction fees on most Fidelity mutual funds. Individual fund expense ratios still apply, and fees can apply to less common activities. Verify the current fee schedule on fidelity.com. For how fees show up on workplace plans, see our guide to the Fidelity record-keeping fee.
How to Open a Solo 401(k) at Fidelity
- Confirm you qualify. No employees other than you and your spouse, and earned income from the business.
- Gather your details. Many providers ask for an Employer Identification Number (EIN), business information and your spouse’s details if you are married.
- Start the application on fidelity.com. Search for the self-employed 401(k) from the retirement section of the site. If you do not meet the online criteria you will be directed to paper forms.
- Complete and sign the plan documents. The adoption agreement and trust agreement are the plan’s legal documents. Keep copies.
- Fund the account. After approval you can contribute from your bank, or roll over eligible pre-tax retirement money if the plan accepts it.
- Pick investments. Cash does not invest itself. A low-cost index fund is a common starting point for a simple portfolio.
- Track your deadlines and filings. See below.
Only use phone numbers and forms from your own Fidelity account or fidelity.com. Search results for these topics are full of fake “support” numbers.
Deadlines, Taxes and Paperwork
- Employer contributions for a self-employed owner are generally due by your business tax filing deadline, including extensions.
- Employee deferrals: SECURE 2.0 lets a sole proprietor with no employees adopt a new plan after year-end, up to the tax filing deadline, and still make employee deferrals for the prior year. Confirm timing with a tax professional before relying on this.
- Taxes: If you are unincorporated, contributions are generally deducted on your personal return. If you are incorporated, they are generally a business expense.
- Form 5500-EZ: A one-participant plan generally must file this form each year once plan assets reach $250,000 at year-end.
- Excess contributions: Withdraw excess deferrals by the following Tax Day to avoid being taxed twice.
The 2026 Roth catch-up rule for people with more than $150,000 of prior-year W-2 wages is based on wages from the employer sponsoring the plan, so it generally does not affect a self-employed owner who pays themselves no wages. If you pay yourself a W-2 salary from an S corporation, ask your tax professional whether it applies.
Frequently Asked Questions
Does Fidelity offer a solo 401(k)?
Yes. Fidelity offers a self-employed 401(k) for owner-only businesses, and you can open it online if you meet its criteria.
Is the Fidelity solo 401(k) free?
Fidelity has been reported to charge no setup or recurring maintenance fee. Fund expenses and fees for less common activities can still apply. Check the current fee schedule.
Can I contribute to a Roth solo 401(k) at Fidelity?
Tax law allows Roth deferrals in a solo 401(k), but whether Fidelity’s plan offers them depends on its plan documents. Check the adoption agreement.
Can I have a solo 401(k) and a 401(k) at my day job?
Yes, if you have self-employed income. Your employee deferrals to both plans share one $24,500 limit in 2026, but you can make employer contributions to the solo plan separately, subject to the combined limit for that plan.
Can my spouse contribute?
If your spouse works in the business and earns income from it, they can participate and make their own deferrals and employer contributions.
When should I open the plan?
Before you want to make employee deferrals, ideally before year-end. SECURE 2.0 allows later adoption for some sole proprietors, but confirm with a tax professional.
How do I log in to my Fidelity solo 401(k)?
It appears as an account when you log in to your Fidelity.com account. Only use the official site, and never call a number from a search result.
Do I need a solo 401(k) calculator?
The worked examples above use the IRS formula. Fidelity also has a small business retirement plan contribution calculator on its website, and your tax professional can run the numbers.
UseFidelity.com is an independent site and is not affiliated with Fidelity Investments. This article is general information, not tax, legal or investment advice. Figures last checked 3 November 2026.
Sources
- IRS: One-participant 401(k) plans
- Fidelity Learning Center: Solo 401(k) contribution limits
- White Coat Investor: How to Open a Solo 401(k) at Fidelity (Fidelity application process and fees, last updated April 2026)
- IRS Notice 2025-67 (2026 limits). 2027 figures are projections.