Solo 401(k) for the Self-Employed: How It Works

TL;DR: A Solo 401(k), also called a one-participant 401(k), is a workplace retirement plan for a business owner with no employees other than a spouse. It lets the owner contribute in two capacities, once as an employee through an elective deferral of up to $24,500 for 2026, and once as the employer through a profit-sharing style contribution, for a combined 2026 annual-additions limit of $72,000, or up to $83,250 for savers who turn 60 to 63 during the year. This is educational information, not individualized tax, legal, or financial advice.

A Solo 401(k) Is a One-Participant Plan for Self-Employed Owners With No Other Employees

A Solo 401(k), what the Internal Revenue Service calls a one-participant 401(k), is a traditional 401(k) plan built for a business owner who has no employees other than a spouse.

The Internal Revenue Service describes it as “a traditional 401(k) plan covering a business owner with no employees, or that person and his or her spouse.” Structurally and for tax purposes it is a genuine 401(k), but because there are no other workers whose participation could create an imbalance, it skips the nondiscrimination testing larger 401(k) plans must run every year. That simplified status ends the moment the business hires a common-law employee who is not the owner’s spouse.

A sole proprietor, an independent contractor operating as a single-member LLC, a freelancer, and a husband-and-wife business can all qualify for a Solo 401(k), as long as the only people drawing pay from the business are the owner and, if applicable, a spouse who also earns income from it.

The Owner Contributes in Two Capacities, Employee and Employer

A Solo 401(k) owner can make two separate types of contribution to the same account in the same year, and combining both is what allows the plan to hold far more than a typical IRA.

The IRS frames the structure directly: the business owner “wears two hats” in a one-participant 401(k), one as the employee making an elective deferral and one as the employer making a nonelective, profit-sharing style contribution, and contributions can be made in both capacities. The employee side works like a standard workplace 401(k) deferral, capped at $24,500 for 2026. The employer side is calculated as a percentage of compensation, generally up to 25%, using the specific earned-income computation for the self-employed set out in IRS Publication 560. The two pieces are added together, and the combined total cannot exceed the overall annual-additions ceiling in Internal Revenue Code section 415(c), which is $72,000 for 2026, or 100% of compensation if that is less.

The 2026 Solo 401(k) Contribution Limits

For 2026, a Solo 401(k) owner under 50 can reach $72,000 in total annual additions, and catch-up contributions raise that ceiling to $80,000 at age 50 and older, or $83,250 for savers who turn 60 to 63 during the year.

2026 figure	Amount
Employee elective deferral (IRC section 402(g))	$24,500
Combined annual-additions cap, employee plus employer (IRC section 415(c))	$72,000
Age-50 catch-up	$8,000 (total up to $80,000)
Ages 60-63 catch-up	$11,250 (total up to $83,250)

Catch-up contributions sit on top of the $72,000 annual-additions figure. They are not counted inside it, and both figures apply specifically to the 2026 tax year, since these dollar limits move with inflation and are republished annually.

For context, a SEP IRA, the other common self-employed retirement plan, caps out at the lesser of 25% of compensation or $72,000 for 2026, with no employee-deferral piece and no catch-up at all. That gap is the core reason a Solo 401(k) usually beats a SEP IRA on total contribution room, a comparison covered in full further down. For a broader look at how a Solo 401(k) fits alongside other account types, start with the IRAInvesting home page.

Setting Up and Funding a Solo 401(k): The Practical Steps

Opening and funding a Solo 401(k) follows a sequence: confirm eligibility, select a provider and plan document, elect and make the employee deferral, calculate and make the employer contribution, and track the paperwork the plan requires as it grows.

Confirm eligibility first. The business must have no common-law employees other than the owner and, if applicable, a spouse who also earns income from the business. Hiring an outside employee ends the plan’s simplified, one-participant status.
Choose a provider and review the plan document closely. The document, not the marketing page, determines which optional features the plan actually offers, including a Roth option, loans, and after-tax contributions. Confirm each feature in writing before opening the account.
Elect and make the employee elective deferral. This functions like a standard workplace 401(k) deferral, up to $24,500 for 2026, and is separate from the employer contribution.
Calculate and make the employer nonelective contribution. This piece is figured as a share of compensation, generally up to 25%, using the specific earned-income computation for the self-employed described in IRS Publication 560, and the combined total with the employee deferral cannot exceed the $72,000 annual-additions cap (or $80,000 to $83,250 with the applicable catch-up).
Track the account as it grows and watch the filing threshold. A one-participant plan generally must file Form 5500-EZ once plan assets reach $250,000 at year-end. A contribution-tracking habit that logs both the employee and employer pieces across the year makes that threshold, and the annual-additions cap itself, easier to see coming.

The Roth Solo 401(k) Option

A Solo 401(k) can offer a Roth option for the employee elective-deferral piece, if the plan document provides for it, so contributions go in after-tax and qualified withdrawals come out tax-free later.

Because a Solo 401(k) is a genuine 401(k), it can permit designated Roth contributions the same way a large employer’s plan can, but only if the specific plan document allows it. Some prototype Solo 401(k) documents do not offer a Roth option at all, so confirm the feature in writing before assuming it applies. Where it is offered, the Roth ceiling equals the elective-deferral limit, $24,500 for 2026, which is far above the $7,500 an individual can put into a Roth IRA, and unlike a Roth IRA, the designated Roth account inside a 401(k) carries no income-based eligibility limit. Since 2024, designated Roth accounts inside a 401(k) are also no longer subject to lifetime required minimum distributions, a change enacted by the SECURE 2.0 Act that aligned the Roth 401(k) with the Roth IRA on that point.

Solo 401(k) Loans

Many, though not all, Solo 401(k) plan documents allow the owner to borrow from the account, generally up to the lesser of $50,000 or 50% of the vested balance.

Plan loans are governed by Internal Revenue Code section 72(p), and a loan that meets the statutory exception is not treated as a taxable distribution. Loans generally must be repaid within five years in level payments made at least quarterly, with a longer repayment window available for a loan used to buy a principal residence. This is a meaningful contrast with an IRA, where borrowing from the account at all is a prohibited transaction that can disqualify the entire IRA. Whether a Solo 401(k) offers loans at all depends entirely on the plan document, and many prototype Solo 401(k) documents skip the feature, so confirm it directly with the provider rather than assuming it is included.

The Rule of 55

A Solo 401(k) participant who separates from service in or after the year they turn 55 can take penalty-free distributions from the plan, an exception that is not available from an IRA.

The 10% additional tax on early distributions does not apply to a distribution from a plan such as a 401(k), made to an employee after separation from service during or after the year the employee turns 55, under Internal Revenue Code section 72(t). The same exception explicitly does not apply to IRAs, which means rolling a 401(k) balance into an IRA before age 59 and a half can forfeit access to it. How “separation from service” applies when the account holder also owns the business is a fact-specific question the plan document and a tax professional should confirm before anyone relies on this exception.

Creditor Protection Carries an Important Nuance for Owner-Only Plans

A standard 401(k) covered by ERISA carries broad protection from creditors and bankruptcy, but a Solo 401(k) covering only the owner and a spouse is generally not an ERISA-covered plan, so that protection may not automatically extend to it.

The federal law behind 401(k) creditor protection is the anti-alienation provision at 29 U.S.C. section 1056(d)(1), which requires that a pension plan provide that benefits under it may not be assigned or alienated. The U.S. Supreme Court, in Patterson v. Shumate, held that this provision keeps a qualified plan’s assets out of the bankruptcy estate entirely, with no dollar cap, aside from recognized exceptions such as a qualified domestic relations order or a federal tax levy. The nuance for a Solo 401(k) is that an owner-only plan, covering just the owner or the owner and a spouse with no other common-law employees, is generally not considered an ERISA-covered plan in the first place, so its creditor protection outside bankruptcy then depends on state law instead. Confirm this with counsel rather than assuming it, especially before relying on it for asset-protection planning. By comparison, an IRA’s bankruptcy protection is capped at $1,711,975 for cases filed between April 1, 2025 and March 31, 2028, and its protection outside bankruptcy is governed entirely by state exemption law, which varies widely.

Solo 401(k) vs. SEP IRA for the Self-Employed

For the same self-employment income, a Solo 401(k) generally allows a larger total contribution than a SEP IRA, because the Solo 401(k) adds a full employee elective deferral on top of the employer-side contribution, while a SEP IRA is funded by the employer only.

SEP plans are funded entirely by employer contributions, with no employee-deferral piece and no catch-up contribution of any kind, since a catch-up only applies to employee elective deferrals. For 2026, the SEP maximum is the lesser of 25% of compensation or $72,000, the same headline ceiling that caps the employer side of a Solo 401(k), but the SEP has no equivalent to the Solo 401(k)’s employee deferral, which is where the Solo 401(k)’s extra room comes from. A Solo 401(k) can also offer a Roth option and, if the plan document allows, loans, features a traditional SEP historically did not offer, though the SECURE 2.0 Act now permits a Roth SEP if the specific arrangement provides for it. The trade-off runs the other way too. A SEP is generally simpler to administer and can be established later in the year than many providers allow for a new Solo 401(k), so a saver weighing the two should factor in administrative simplicity alongside contribution capacity. For the full comparison, see our dedicated SEP IRA guide.

Frequently Asked Questions

Who qualifies for a Solo 401(k)? A business owner with no common-law employees other than a spouse who also earns income from the business. A sole proprietor, a single-member LLC, and a husband-and-wife business can all qualify. Hiring an outside employee ends the plan’s simplified status.

What is the 2026 Solo 401(k) contribution limit? Up to $72,000 in total annual additions for a saver under 50, combining the $24,500 employee elective deferral with the employer contribution. Catch-up contributions raise the total to $80,000 at age 50 and older, or $83,250 for savers who turn 60 to 63 during the year.

Can a Solo 401(k) owner also have a SEP IRA? This article does not resolve that question, since it depends on plan-specific and aggregation rules a tax professional should review for your situation. What the two plans do differ on is capacity: the Solo 401(k) generally allows a larger total contribution because it adds an employee deferral on top of the employer share, while the SEP is employer-funded only.

Does a Solo 401(k) allow Roth contributions? Only if the specific plan document provides for it. Where offered, the Roth portion is capped at the elective-deferral limit, $24,500 for 2026, with no income-based eligibility limit and, since 2024, no lifetime required minimum distributions.

Is a Solo 401(k) protected from creditors the same way a regular 401(k) is? Not automatically. A Solo 401(k) covering only the owner and a spouse is generally not an ERISA-covered plan, so the federal anti-alienation protection that shields most 401(k)s may not apply, and the account’s protection then depends on state law. Confirm the specifics with a qualified attorney before relying on this for asset-protection planning.

Always consult your own legal, financial, and tax professionals before opening or changing a retirement account.

By Tim Schmidt + Sean Webster Reviewed by Sean Webster