Self-Directed Solo 401(k): Limits, Investments, and Setup

A self-directed Solo 401(k) is a one-participant 401(k) plan for self-employed people and owner-only businesses that pairs the high contribution ceilings of a workplace 401(k) with the freedom to hold alternative assets like real estate, private equity, and precious metals. For 2026, you can defer up to $24,500 as an employee contribution and add an employer profit-sharing contribution of up to 25% of net self-employment earnings.¹ The IRS treats it as a “one-participant 401(k) plan,” and the same rules that govern any 401(k) apply.²

Who Qualifies

You qualify if you earn self-employment income from a trade or business and have no full-time employees other than yourself and, optionally, your spouse. Your income can come from freelancing, consulting, a sole proprietorship, an LLC, an S-Corporation, or another pass-through entity. It has to be active self-employment income. Passive dividends and rental income from property you don’t actively manage don’t count.

The headcount limit is the rule that trips people up. If you hire someone who works more than 1,000 hours in a calendar year, you lose the simplified Solo 401(k) structure and fall under the testing and reporting rules for multi-participant plans. Part-time workers under that threshold and independent contractors don’t count. A spouse who works in the business can participate as a second employee and make their own contributions, which effectively doubles what a household can save.

2026 Contribution Limits

Contributions have two components because you play two roles. As the employee, you can defer up to $24,500 of earned income in 2026.¹ As the employer, you can add a profit-sharing contribution of up to 25% of your net self-employment earnings.² Combined contributions cannot exceed 100% of your earned income.

If you’re 50 or older, you can add a catch-up contribution of $8,000 in 2026. SECURE 2.0 created a larger catch-up for participants aged 60 through 63 of $11,250 for 2026 instead of $8,000.¹ In that four-year window, employee deferrals alone can reach $35,750 before any employer contribution.

How the Employer Contribution Actually Calculates

The employer side is less generous than it sounds. For this purpose, “earned income” is your net self-employment earnings after subtracting half of your self-employment tax and the employer contribution itself.² Because the contribution reduces the base it’s calculated on, the effective employer rate for sole proprietors and single-member LLCs works out to roughly 20% of net business profit, not a full 25%. S-Corporation owners run the math differently: their employer contribution is based on the W-2 salary the corporation pays them, and 25% applies directly to that salary.

Roth Option

Many Solo 401(k) plans let you designate employee deferrals as Roth, meaning you contribute after-tax dollars and qualified withdrawals later come out tax-free.³ The $24,500 deferral limit applies whether you go pre-tax or Roth, and you can split between the two. Under SECURE 2.0, plans can also allow employer profit-sharing contributions to be designated as Roth, though those amounts are taxable in the year contributed.⁴

Setup and Funding Deadlines

Timing separates Solo 401(k)s from SEP IRAs, and missing a date can cost you a full year of contributions. To make both employee deferrals and employer contributions for a given tax year, the plan generally has to be established by December 31 of that year. Set it up after year-end but before your tax filing deadline, and you can still make employer profit-sharing contributions, but you may lose the ability to make employee deferrals for that year.⁵

Once the plan exists, the deadline to fund both employee deferrals and employer contributions is your business’s tax filing deadline, including extensions.³ Sole proprietors filing Schedule C get to April 15, or October 15 with an extension. S-Corps filing Form 1120-S have a March 15 deadline, extendable to September 15. The salary deferral election itself generally has to be made by the business’s year-end for the year the deferrals begin.

Excess Deferrals

If your total employee deferrals exceed the annual limit, the excess must be distributed back to you by April 15 of the following year. Corrected on time, the excess is taxed once in the year deferred, and the related earnings are taxed in the year distributed. Miss April 15 and the excess gets taxed twice: once in the year contributed, and again when eventually distributed. Late corrective distributions can also trigger the 10% early withdrawal penalty and mandatory 20% withholding.⁶ This shows up most often when someone contributes to a W-2 employer’s 401(k) and their own Solo 401(k) in the same year, since the deferral limit is a single limit across all your 401(k) plans combined.

What You Can Invest In

The “self-directed” part is the reason most people choose this plan over a standard brokerage 401(k). Beyond stocks, bonds, and mutual funds, the plan can hold residential rental property, commercial real estate, undeveloped land, private equity, private placements, and cryptocurrency.

Precious metals like gold and silver are allowed, but they have to meet IRS fineness standards. Gold bullion, for example, must be at least 99.5% pure, and a bank or approved trustee must hold physical possession.⁷ Many self-directed providers structure the plan with a dedicated checking account tied to the plan’s own EIN, so you can write checks or wire funds to close on investments without waiting on a custodian.

Prohibited Investments and Transactions

Federal law bars certain assets outright. Collectibles like artwork, antique rugs, stamps, gems, and most coins can’t be held in the plan.⁸ The precious-metals exception is narrow; random gold coins or jewelry don’t qualify.

The bigger risk is prohibited transactions. Under IRC Section 4975, you cannot buy, sell, lease, or exchange property between the plan and a “disqualified person.” Disqualified persons include you, your spouse, your parents, your children and their spouses, and any entity they control.⁹ Plan assets cannot be used for your personal benefit, even indirectly. Renting a plan-owned property to your family, having your son manage a plan-owned rental, or lending plan money to your business all qualify.

The penalty is an excise tax of 15% of the amount involved for each year the transaction remains uncorrected. If it still isn’t fixed by the end of the taxable period, a second-tier tax of 100% of the amount involved applies.⁹ A Solo 401(k) faces the excise route rather than the automatic full-account disqualification that hits self-directed IRAs, but the IRS can still disqualify a plan under separate correction procedures if problems aren’t resolved.¹⁰

The Real Estate Leverage Advantage

One of the most underappreciated reasons to use a Solo 401(k) rather than a self-directed IRA is how it handles debt-financed real estate. When a retirement plan borrows money to buy property, the income attributable to the borrowed portion is normally hit with Unrelated Debt-Financed Income tax. IRAs using non-recourse loans owe this tax on a proportional share of rental income and sale proceeds.

Solo 401(k) plans are exempt under IRC Section 514(c)(9), which treats a qualified trust under Section 401 as a “qualified organization” whose debt-financed real estate income is not treated as acquisition indebtedness.¹¹ The exemption applies as long as the purchase price is fixed at the time of the deal, loan payments aren’t tied to the property’s income, the property isn’t leased back to the seller, and the seller didn’t also provide the financing. If you’re planning to buy rental property with leverage inside a retirement account, this alone can be reason enough to use a Solo 401(k).

Borrowing From the Plan

If your plan document includes a loan provision, you can borrow from your own account without triggering taxes or penalties. The maximum is the lesser of $50,000 or 50% of your vested balance. If 50% of your balance is under $10,000, you can still borrow up to $10,000.¹²

Repayments have to be made in substantially equal installments at least quarterly, and the loan has to be repaid within five years unless the money was used to buy your primary residence.¹² Interest goes back into your own account. Default and the outstanding balance is treated as a distribution, subject to income tax and potentially the 10% early withdrawal penalty.

Distributions and Required Minimums

Withdrawals from a traditional pre-tax Solo 401(k) before age 59½ are subject to ordinary income tax plus a 10% additional early distribution tax.¹³ Several exceptions remove the 10% penalty:

Total and permanent disability of the participant.
A series of substantially equal periodic payments calculated under IRS-approved methods.
Unreimbursed medical expenses over 7.5% of adjusted gross income.
Up to $22,000 for qualified federally declared disaster losses.
One personal or family emergency distribution per calendar year up to $1,000, available after December 31, 2023, under SECURE 2.0.

Qualified Roth 401(k) distributions come out entirely tax-free, including earnings. A distribution qualifies if it happens at least five years after your first Roth contribution to the plan and after you reach 59½.

Required minimum distributions generally begin at age 73.¹⁴ Employees of a company can sometimes delay RMDs past 73 if they’re still working, but Solo 401(k) owners almost never qualify because the exception doesn’t apply to anyone owning more than 5% of the business. Starting in 2024, designated Roth balances in 401(k) plans are no longer subject to RMDs during the owner’s lifetime.

Setting Up the Plan

Start by obtaining an Employer Identification Number specifically for the plan. This is separate from your business’s existing EIN. The IRS issues plan EINs online at no cost, usually within minutes.¹⁵

Then complete two documents: an Adoption Agreement and a Basic Plan Document. The Adoption Agreement specifies your plan name, plan year, contribution types allowed, and the plan administrator. The Basic Plan Document contains the operational rules for contributions, distributions, loans, and vesting. Most Solo 401(k) providers supply pre-approved versions of both. Open a dedicated bank or brokerage account in the plan’s name using the plan’s EIN; this becomes the hub for contributions and investment transactions.

You can fund the plan through new contributions from business earnings, a direct rollover from an existing IRA, or a rollover from a former employer’s 401(k).¹⁶ Process any rollover as a direct trustee-to-trustee transfer to avoid the mandatory 20% withholding that hits indirect rollovers from qualified plans.

Annual Form 5500-EZ Filing

Reporting is lighter than for multi-participant plans, but not zero. Once total plan assets exceed $250,000 at the end of the plan year, you have to file Form 5500-EZ with the IRS.¹⁷ Plans under that threshold are exempt unless it’s the plan’s final year. The $250,000 threshold is measured across all one-participant plans you maintain, not one account.

The deadline is the last day of the seventh month after the plan year ends, which is July 31 for calendar-year plans.¹⁸ You can extend to October 15 by filing Form 5558. Don’t ignore this. The penalty for a late Form 5500-EZ is $250 per day, up to $150,000 per return, plus interest.¹⁹ If you’ve missed past filings, the IRS offers a penalty relief program for late filers, but only if you file before the IRS contacts you.

You also have to file a final Form 5500-EZ when you terminate the plan, regardless of asset balance. Keeping clean records of contributions, distributions, asset valuations, and any plan loans throughout the year keeps this annual filing simple and protects you in an audit.

1
Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
2
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3
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4
Internal Revenue Service. SECURE 2.0 Act Changes Affect How Businesses Complete Forms W-2
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Fidelity Investments. Self-Employed 401(k) Plan Overview
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Internal Revenue Service. 401(k) Plan Fix-It Guide – Elective Deferrals Werent Limited to the Amounts Under IRC Section 402(g)
7
Internal Revenue Service. Investments in Collectibles in Individually Directed Qualified Plan Accounts
8
Internal Revenue Service. Retirement Topics – Plan Assets
9
Office of the Law Revision Counsel. 26 USC 4975 – Tax on Prohibited Transactions
10
Internal Revenue Service. Retirement Topics – Prohibited Transactions
11
Office of the Law Revision Counsel. 26 US Code 514 – Unrelated Debt-Financed Income
12
Internal Revenue Service. Retirement Plans FAQs Regarding Loans
13
Internal Revenue Service. Retirement Topics – Exceptions to Tax on Early Distributions
14
Internal Revenue Service. Retirement Topics – Required Minimum Distributions (RMDs)
15
Internal Revenue Service. Get an Employer Identification Number
16
Internal Revenue Service. Rollovers of Retirement Plan and IRA Distributions
17
Internal Revenue Service. Instructions for Form 5500-EZ
18
Internal Revenue Service. Form 5500 Corner
19
Internal Revenue Service. Penalty Relief Program for Form 5500-EZ Late Filers