A Solo 401(k) is the most powerful retirement account available to a self-employed person with no staff. In 2026 you can contribute up to $70,000, choose a Roth track for part of it, and potentially take a loan — all without the complications of a multi-employee plan. The tradeoff: you must open it before December 31 of the year you want to use it. Here is how to do it right.
What changed in 2026
- Employee deferral limit rose to $23,500 (up from $23,000 in 2024), with a catch-up of $7,500 for those 50+ and a new enhanced catch-up of $11,250 for ages 60–63 under SECURE 2.0.
- Total combined limit hit $70,000 (employee + employer contributions, not counting catch-ups).
- Roth deferrals became standard — nearly every major brokerage now offers a Roth solo 401(k) track in the same account, letting you split traditional and Roth contributions year by year.
- Form 5500-EZ threshold stayed at $250,000 — only file the form if your plan assets exceed that figure.
How the two contribution buckets work
A Solo 401(k) has two distinct contribution pools:
| Bucket |
Role |
2026 Limit |
| Employee salary deferral |
You as the employee |
Up to $23,500 (plus catch-up) |
| Employer profit-sharing |
You as the employer |
Up to 25% of W-2 wages or ~20% of net SE income |
| Combined max |
Total (both buckets) |
$70,000 (plus catch-ups) |
At moderate income, the employee deferral lets a Solo 401(k) beat a SEP IRA on contribution room — because you can front-load the deferral even if profit-sharing math is small.
Example: A freelancer with $60,000 net SE income can defer ~$23,500 as employee + ~$11,000 as employer = ~$34,500 total. A SEP IRA would cap at ~$11,000 (20% of income). Big difference.
Who qualifies
- Self-employed individuals with zero full-time W-2 employees (other than a spouse).
- Sole proprietors, single-member LLCs, partnerships, S-corps.
- Part-time or seasonal contractors you hire do not count if they work fewer than 1,000 hours per year and are under 21 — but confirm current IRS rules before assuming.
How to open a Solo 401(k): step by step
- Choose a provider. Fidelity (free, Roth option, broad funds), Schwab (similar), and Vanguard (limited Roth option) are the main free choices. For maximum flexibility — including alternative investments — a self-directed custodian charges fees but adds options most solo earners do not need.
- Apply online. Select "Individual 401(k)" or "Solo 401(k)." You will need your EIN (Employer Identification Number) — get a free one at IRS.gov if you do not have one.
- Sign the plan adoption agreement. This is a legal document establishing your plan. Brokerages provide a standard version.
- Do this before December 31 of the tax year you want contributions to apply to. This deadline is hard — unlike a SEP IRA, you cannot open a Solo 401(k) retroactively.
- Make employee deferrals by December 31. Employer profit-sharing contributions can be made up to your tax filing deadline (including extensions).
- Invest. Choose funds — a simple three-fund portfolio or a target-date fund works well.
Solo 401(k) vs SEP IRA: when each wins
| Situation |
Better choice |
| Net SE income under ~$100,000 |
Solo 401(k) — employee deferral adds room |
| Want a Roth option |
Solo 401(k) |
| Want loan access |
Solo 401(k) |
| Simplest possible setup |
SEP IRA |
| High income, want max simplicity |
Either — limits converge |
| Have or plan to hire staff |
SEP IRA (or switch to a full plan) |
See How to start a SEP IRA in 2026 for the full comparison.
How to pick your contribution split
Traditional vs. Roth deferral is a tax-timing decision:
- Traditional: deduct now, pay tax on withdrawal in retirement. Best if you expect your tax rate to fall.
- Roth: no deduction now, tax-free in retirement. Best if you expect your tax rate to stay the same or rise — or if you want tax diversification.
Many people split: max the traditional employer bucket (guaranteed deduction) and put employee deferrals into Roth when income is moderate. See How to do a Roth conversion in 2026 for the broader strategy.
Common mistakes
Missing the December 31 deadline. You cannot establish a Solo 401(k) after year-end for that year. Set a calendar reminder in November.
Forgetting to get an EIN. Most brokerages require one. Takes five minutes at IRS.gov.
Only making employee deferrals. You also get an employer profit-sharing contribution on top — don't leave that on the table.
Not signing the plan documents before the deadline. The plan must be formally adopted, not just the account opened. Confirm with your brokerage.
Hiring a full-time employee later without converting. If you hire someone who qualifies, your Solo 401(k) must become a full plan — see a benefits consultant.
What to skip
- Complex self-directed plans for alternative assets unless you have specific, researched reasons. Most solo earners benefit from simple index funds inside a free brokerage plan.
- Third-party plan administrators charging $500–$1,000/year to manage a plan that Fidelity offers free.
- Waiting until tax season — by then, you've lost the year's contribution opportunity for employee deferrals.
FAQ
Can I have a Solo 401(k) and an IRA?
Yes. You can contribute to both in the same year, subject to each account's separate limits and income rules.
Can my spouse contribute?
Yes, if they earn income from the same business. A spousal Solo 401(k) effectively doubles the household contribution room.
When do I need to file Form 5500-EZ?
When plan assets exceed $250,000 at year-end. The form is simple, but missing the deadline (July 31) has penalties.
Can I take a loan from my Solo 401(k)?
Yes — up to 50% of your vested balance or $50,000, whichever is less. Repaid with interest to yourself. Fidelity and Schwab support this.
Where to go next
See How to start a SEP IRA in 2026, How to do a Roth conversion in 2026, and How to harvest tax losses yourself in 2026.