If you are self-employed with no employees other than a spouse, a Solo 401(k) lets you contribute as both the employee and the employer. That double-hat structure is what pushes the annual cap to $70,000 in 2026 [VERIFY]. With a self-directed provider, you can also hold Bitcoin inside it. This is the single most powerful account most self-employed people never open.
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Not a CPA or financial advisor. This is education, not tax or investment advice. Contribution limits and eligibility change. Anything marked [VERIFY] needs confirmation against current IRS publications before you act.
A Solo 401(k) is a 401(k) built for a business with one employee (you) and maybe a spouse. Because you wear both hats, you contribute twice: up to $23,500 as the employee and up to ~25% of net self-employment income as the employer, capped at $70,000 combined [VERIFY]. Most major brokerages offer a free traditional Solo 401(k). Self-directed providers let you hold Bitcoin and alternative assets. Open one, fund it, and you just legally removed tens of thousands of dollars from your taxable income.
A Solo 401(k), also called a one-participant 401(k) or a Solo-K, is a qualified retirement plan designed for self-employed individuals with no employees other than a spouse. Freelancers, sole proprietors, single-member LLCs, 1099 consultants, Schedule C filers, and small-business owners with no W-2 staff all qualify.
The structural trick is this: the IRS treats you as two separate parties to the plan. You are the employee (you can make elective deferrals out of your compensation) and you are the employer (you can make a profit-sharing contribution on top). No W-2 employee at a regular company gets to do that. This is what makes the Solo 401(k) so much more powerful than an IRA or a SEP at moderate income.
Who qualifies: self-employed with zero non-spouse employees. Hire one W-2 employee and you must convert to a standard 401(k) plan with full ERISA coverage rules. A spouse on payroll is the one allowed exception and actually lets you double up on contributions.
Three numbers matter:
The elective deferral is a total across all 401(k)-type plans you participate in. If you also have a W-2 day job with a 401(k) and you max it there, you cannot add more employee deferral on the Solo 401(k) side. The employer contribution is separate and per-business, so a side-hustle Solo 401(k) still works to shelter self-employment income even if your day-job 401(k) is maxed.
Consultant, sole proprietor, $150,000 net self-employment income in 2026 [VERIFY]:
Employee deferral: $23,500.
Employer contribution: roughly 20% of net SE income after the SE-tax adjustment, around $27,700.
Total: approximately $51,200 legally removed from the current year's taxable income.
At a 24% marginal federal rate plus 5% state, that is roughly $14,800 in tax saved this year alone. Do that for fifteen years and you have shifted the equivalent of several starter houses out of the tax stream and into a compounding retirement balance. The contribution is a deductible business expense, which also reduces self-employment tax in some structures.
Most major providers now offer a Roth bucket inside the Solo 401(k). You can split your employee elective deferral between traditional (pre-tax) and Roth (after-tax) in any ratio. The employer profit-sharing contribution must be traditional pre-tax under most plan designs [VERIFY provider specifics].
Post-SECURE 2.0, the employer contribution can also be designated Roth at the participant's election if the plan allows it. Support for that feature is still uneven across providers as of 2026 [VERIFY]. If you want both a Roth bucket and the full $70K combined cap with the employer piece also Roth, you likely need a specialty provider rather than a free Fidelity-style plan.
The free Solo 401(k) offered by Fidelity, Vanguard, and Schwab gives you access to the brokerage's normal lineup: stocks, ETFs, mutual funds. Spot Bitcoin ETFs (IBIT, FBTC, and similar) are investable inside those accounts. That is the simplest path to Bitcoin exposure in a Solo 401(k).
For native Bitcoin (your own keys, or exchange custody without an ETF wrapper), use a self-directed Solo 401(k) provider. Current options include Alto CryptoIRA, iTrustCapital, Rocket Dollar, and a handful of others [VERIFY]. Fees are higher than the free brokerages (often $500-1,500/yr in setup and ongoing fees, plus trading spreads).
A few providers support a "Checkbook IRA LLC" structure, where the plan owns an LLC and the LLC holds a self-custodied wallet. That unlocks full self-custody inside the retirement wrapper, at the cost of more paperwork and stricter prohibited-transaction rules. This is a real strategy but also a footgun zone. If you run afoul of the prohibited transaction rules, the IRS can disqualify the entire plan.
The Solo 401(k) wins on most axes once you understand it. SEP-IRA wins on simplicity.
See /accounts/sep-ira/ for the other side of the comparison.
In rough order of utility:
Open the plan by December 31 of the tax year you want to contribute for. Elective deferrals must be formally elected by year-end as well, even if funded later. Employer profit-sharing contributions can be funded up until the tax filing deadline (including extensions) for the prior year.
Once total plan assets exceed $250,000 at year-end, file Form 5500-EZ annually [VERIFY]. It is a one-page form. Late-filing penalties are brutal, so set a calendar reminder.
Last updated 2026-04-14. Not tax or legal advice.