Retirement and tax-advantaged accounts · Overview

Solo 401(k).
The self-employed superweapon.

READ8 min·UPDATED2026-09-27·APPLIES TOUnited States·LEVELIntermediate

For self-employed people wanting maximum retirement contributions. Sources are listed at the bottom of the page; check their dates before acting.

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 $72,000 in 2026. 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.

This page covers US-specific accounts and tax law. Outside the US? The priority order is the same, the account names differ (ISA in the UK, TFSA/RRSP in Canada, Super in Australia, etc.).

Not a CPA or financial advisor. This is education, not tax or investment advice. Contribution limits and eligibility change. Specific figures should be confirmed against current IRS publications before you act on them.

Short answer

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 $24,500 as the employee and up to ~25% of net self-employment income as the employer, capped at $72,000 combined. The highest contribution limit available to a self-employed person outside a defined-benefit pension plan. 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 legally removed tens of thousands of dollars from your taxable income.

On this page

What a Solo 401(k) is
The 2026 limits
Worked example
Roth Solo 401(k) option
Bitcoin inside a Solo 401(k)
Tradeoffs vs a SEP-IRA
Providers
Paperwork requirements

What a Solo 401(k) is

A Solo 401(k), also called a one-participant 401(k) or a Solo-K, is a qualified retirement plan designed for self-employed people 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.

Any self-employed person with no full-time employees (other than a spouse) verify×DON'T TRUST, VERIFYClaim: Solo 401(k) requires self-employment with no full-time employees other than spouse.Verify at: IRS One-Participant 401(k) ↗ Source 1 in the list belowOnce you hire a full-time employee (excluding spouse), the plan must convert to a standard 401(k)..

Includes: freelancers, consultants, independent contractors, sole proprietors, single-member LLCs, S-corp owners, side-gig income.

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 lets you double up on contributions.

The 2026 limits

Three numbers matter:

Employee elective deferral: $24,500 for 2026. Same as any other 401(k). Can be split between traditional and Roth buckets.
Employer profit-sharing contribution: up to 25% of net self-employment income (roughly 20% for sole proprietors once you back out the SE tax deduction). Pre-tax under most plan designs.
Combined cap: $72,000 in 2026, across both buckets. Age 50 and over, add an $8,000 catch-up on the employee side ($11,250 at ages 60-63).

The elective deferral is a total across all 401(k)-type plans you participate in verify×DON'T TRUST, VERIFYClaim: 2026 employee 401(k) deferral limit is $24,500, shared across all plans.Verify at: IRS 401(k) limits ↗ Source 2 in the list belowIndexed for inflation.. 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.

COMBINED 2026 LIMIT

$72,000 (under 50) / $80,000 (50+ with catch-up) / $83,250 (ages 60 to 63, with the larger catch-up).

Two buckets, one $72,000 limit in 2026

Employee onlysame as a regular 401(k)

$24,500/yr$72,000/yr limit under 50

Employee + employerunder 50

$24,500/yrUp to 25% of pay

Employee + employerage 50+ except 60 to 63, with catch-up

$24,500/yrUp to 25% of pay

$0$80,000/yr with catch-up

$24,500/yr employee bucket, Traditional or RothUp to 25% of compensation, employer bucket, which can fill the rest of the $72,000/yrCatch-up at 50+, raising the limit to $80,000/yr ($83,250/yr at ages 60 to 63)

Bars show the most each bucket can hold. For a sole proprietor, the 25% works out to 20% of net self-employment income after half the SE-tax deduction.

The employer bucket, up to 25% of compensation, is what lifts a Solo 401(k) past the $24,500 a year employee limit toward the combined 2026 limit of $72,000 a year, or $80,000 at 50+ ($83,250 at ages 60 to 63).

Worked example

Consultant, sole proprietor, $150,000 net self-employment income in 2026:

Employee deferral: $24,500.
Employer contribution: roughly 20% of net SE income after the SE-tax adjustment, around $27,700.
Total: approximately $52,200 legally removed from the current year's taxable income.

At a 24% marginal federal rate plus 5% state, that is roughly $15,100 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 deductible against income tax, but it does not reduce self-employment tax.

Roth Solo 401(k) option

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.

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. If you want both a Roth bucket and the full $72K combined cap with the employer piece also Roth, you likely need a specialty provider rather than a free Fidelity-style plan.

The Mega Backdoor Roth

Some Solo 401(k) plans allow after-tax contributions beyond the $24,500 employee limit (up to the $72,000 combined limit), which can then be converted to Roth inside the plan. Not all plans support this.

Fidelity's Solo 401(k) does not support the Mega Backdoor Roth verify×DON'T TRUST, VERIFYClaim: Fidelity's Solo 401(k) plan document does not support Mega Backdoor Roth conversions.Verify at: Fidelity Solo 401(k) ↗ Source 3 in the list belowCheck current plan document. Features change.. The Mega Backdoor Roth is one of the most powerful tax strategies available to high-income self-employed people.

The Roth option listed for Fidelity under Providers covers Roth deferrals, not after-tax contributions.

Bitcoin inside a Solo 401(k)

The free Solo 401(k) offered by Fidelity 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). See Bitcoin ETF Guide.

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. Fees are higher than the free brokerages (often $500-1,500/yr in setup and ongoing fees, plus trading spreads).

A self-directed Solo 401(k) can hold Bitcoin directly (not via ETF). More complex to set up. Requires a specialized self-directed plan provider. Typically only worth the complexity at large balances ($100k+).

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.

Tradeoffs vs a SEP-IRA

The Solo 401(k) wins on most axes once you understand it. SEP-IRA wins on simplicity.

Higher contribution at low-to-moderate income. The employee $24,500 deferral stacks on top of the 25% employer portion. SEP-IRA is 25% only.
Roth option. Solo 401(k) has one. SEP-IRA does not (Roth SEP exists on paper post-SECURE 2.0 but provider support is still thin).
Loans. A Solo 401(k) allows participant loans up to 50% of balance or $50,000, whichever is less. No loans from a SEP-IRA.
Paperwork. SEP-IRA wins here. Zero annual IRS filing. Solo 401(k) requires Form 5500-EZ once plan assets exceed $250,000.
Backdoor Roth interaction. SEP-IRA balances trigger the pro-rata rule on backdoor Roth conversions. Solo 401(k) balances do not. Material for high earners.

See SEP-IRA: The Simpler Self-Employed Option for the other side of the comparison.

Providers

In rough order of utility:

Fidelity. Free setup and no annual fee. Full brokerage lineup including Bitcoin spot ETFs. Roth option supported. The default recommendation for most self-employed people.
Schwab. Comparable free plans. Slightly thinner Roth and plan-loan feature support at some providers.
Vanguard: no longer offered (sold to Ascensus in 2024).
ETrade. Broader asset mix, allows options and more exotic holdings inside the plan.
MySolo401k, Carry, and similar specialty providers. Paid plans ($500-1,200/yr typical). Worth it when you need full Roth support on the employer contribution, a Checkbook LLC for real estate or crypto self-custody, or other features the free plans do not offer.
Alto, iTrustCapital, Rocket Dollar. Self-directed Solo 401(k) or IRA providers focused on crypto. Higher fees, direct crypto custody on the platform.
Avoid: providers charging high setup or annual fees.

Paperwork requirements

Open the plan by December 31 of the tax year you want to contribute for (a sole proprietor opening a first plan can wait until the unextended filing deadline). 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.

To make employee deferrals for a tax year, a Solo 401(k) must be established by December 31 of that year (sole proprietors, in the plan's first year: by the unextended tax-filing deadline, with those deferrals paid in by then). A plan used only for employer contributions can be established as late as the tax filing deadline (including extensions) verify×DON'T TRUST, VERIFYClaim: Solo 401(k) plan must be established by Dec 31 for employee deferrals (sole proprietor's first year: unextended filing deadline), or by the extended filing deadline for employer-only contributions; contributions can be made until tax filing deadline.Verify at: IRS Solo 401(k) ↗ Source 1 in the list belowSECURE Act 2.0 changed some rules; verify current deadlines..

Once total plan assets exceed $250,000 at year-end, file Form 5500-EZ annually. It is a one-page form. Late-filing penalties are brutal, so set a calendar reminder.

Where to go from here

Do next

Mega Backdoor Roth Capacity

Check how much Roth space is left once the Solo 401(k) is maxed.

Sources

Verify badges in the text link to these sources. Figures, rates and rules change: check each source’s date before acting on it.

IRS - One-participant 401(k) plans - irs.gov ↩
IRS 401(k) limits - irs.gov ↩
Fidelity Solo 401(k) - fidelity.com ↩
IRS Publication 560 - Retirement plans for small business - irs.gov
IRS Form 5500-EZ instructions - irs.gov
SECURE 2.0 Act of 2022 - Roth employer contribution provision - congress.gov

Last updated 2026-09-27. Not tax or legal advice. Disclosures · How pages are reviewed