Buying Rentals in an SDIRA or Solo 401(k): Traps Included

You can buy a rental house with retirement money. The tax code allows it, custodians will set it up, and promoters will tell you it is the smartest thing you can do with an old 401(k). What they spend less time on is the list of things you give up and the single mistake that can turn the whole account into a taxable distribution in one year.

Reviewed against IRS Publication 598 on unrelated business income and IRS prohibited-transaction guidance and IRS one-participant 401(k) guidance on October 1, 2026. Use the instructions for your filing year; the examples are planning illustrations, not a prepared tax return.

Here is the number to hold onto. In the example later in this post, an IRA buys a $250,000 rental with a $100,000 loan, and a debt-financed share of a later sale gain can be taxable to the IRA itself. The illustrative 40% sale case is an assumption, not a percentage locked in by the original down payment. The structure works for a narrow kind of investor. Compare the account-owned and personally owned versions with the actual financing, account rules and taxes before choosing a structure.

The idea: retirement dollars buying rental property

A self-directed IRA (SDIRA) is a regular IRA held at a custodian that permits alternative assets. The tax treatment is identical to any other IRA. The only difference is the menu: instead of mutual funds, the account can hold real estate, notes and private placements. A solo 401(k) is a one-participant employer plan for a self-employed person with no common-law employees eligible to participate other than a spouse, and its plan document can permit the same assets.

In both cases the account is the buyer. Title reads something like "XYZ Trust Company FBO Jane Smith IRA", the account pays the purchase price, and every dollar of rent goes back to the account. You direct the investment. You do not own it, use it or profit from it personally until you take distributions.

The appeal is simple. Rent and appreciation compound with tax deferred in a traditional account, or tax free in a Roth account if the distribution rules are met. For someone with $300,000 sitting in a rollover IRA and no taxable savings, it can look like the only path into rental property.

Whether it is a good path depends on three things: the prohibited transaction rules, the tax on debt inside an IRA, and what the wrapper takes away. Of the four ways a rental makes money, a retirement account neutralizes one completely and taxes another when you borrow.

The prohibited transaction rules that end retirement accounts

The rules come from one idea: the account must invest for its own benefit at arm's length, and never for the current benefit of you or your family. The law enforces that through a list of disqualified persons and a ban on transactions between them and the account.

Disqualified persons include you, your spouse, your lineal ancestors (parents, grandparents) and your lineal descendants (children, grandchildren) along with their spouses. Entities those people control are on the list too, and so are fiduciaries and advisers to the account.

What that rules out in practice:

• Buying a property you or a disqualified person already owns, or selling the account's property to one of them.
• Any personal use. You cannot stay in the beach rental for a weekend, and your daughter cannot rent the duplex unit, even at full market rent.
• Paying a property expense from your own pocket. Every bill, from the tax bill to a $90 plumber visit, is paid by the account. Every rent check is deposited to the account.
• Personally guaranteeing a loan to the account. A guarantee is an extension of credit between you and your plan.
• Paying yourself, or your own management company, to manage the property.
• Doing the work yourself. The conservative reading among practitioners is that the account owner does not supply labor to the property. Hire it out and have the account pay the invoice.

The penalty is what makes this different from ordinary tax mistakes. When an IRA owner engages in a prohibited transaction, the account stops being an IRA as of the first day of that year. The entire balance is treated as distributed at fair market value. On a traditional IRA that means ordinary income tax on the whole account, plus the early distribution penalty if you are under the age threshold. The property does not have to be the whole account for the whole account to be lost.

Qualified-plan prohibited transactions can involve excise taxes and correction obligations; other plan failures can also affect qualification. The IRA-specific automatic-distribution rule should not be treated as the complete penalty framework for a solo 401(k). That is a difference in punishment, not permission. Ask a CPA who works with these plans how the rules apply to yours.

One structure needs a specific caution. The "checkbook control" IRA, where the IRA owns an LLC and you manage the LLC's bank account, removes the custodian from each transaction. It also removes the one party who might have stopped you from paying the wrong bill from the wrong account. The convenience is real and so is the exposure.

UBIT and UDFI: the tax on leveraged IRA real estate

Retirement accounts are tax exempt, with an exception. When a tax-exempt entity earns income through borrowed money, the share of income attributable to the debt is unrelated debt-financed income (UDFI), which is included in the calculation of unrelated business taxable income (UBTI), subject to applicable exclusions and deductions. The tax is often called UBIT. The IRA may need Form 990-T, and any account tax must be handled through the account. Verify the filing threshold and entity treatment rather than assuming no filing is needed merely because deductions eliminate tax.

First, the loan itself. A loan must avoid prohibited extensions of credit, including a personal guarantee by the owner. A non-recourse property loan is a common structure to evaluate; have the custodian and adviser review the actual collateral and remedies. That takes conventional mortgages off the table. Non-recourse lenders are a small group, they underwrite the property's income rather than yours, and as a rule of thumb they ask for much larger down payments than conventional investor loans, often 35% to 50%, at higher rates. Get quotes before you model anything.

Second, the mechanics. The taxable share is roughly the average acquisition debt divided by the property's average adjusted basis for the year. That percentage is applied to income after the same percentage of deductions, including interest and straight-line depreciation. There is a $1,000 specific deduction. What remains is taxed on the trust rate schedule, which reaches its top bracket at a very low level of income. Look up the current schedule; do not assume your personal bracket applies.

Example: a $250,000 rental in an IRA with a $100,000 loan

This is an illustrative example with an assumed 8% non-recourse rate and 25-year amortization.

In year 1 the tax is zero, because interest and depreciation absorb the income. The 40% column is a rounded illustrative assumption, not the required annual computation from opening loan-to-price. Actual UDFI uses average acquisition indebtedness divided by average adjusted basis. Amortization and depreciation change both inputs, and the $1,000 specific deduction applies at the return level rather than once per property. A return can still be required when gross unrelated income reaches the filing threshold, so the account pays for tax preparation either way.

The bite comes later. As interest falls and rent rises, the annual figure turns positive. The larger exposure is the sale. If the debt-financed percentage in the year of sale is 40% and the gain is $100,000, then $40,000 of gain is taxable to the IRA. The sale percentage compares the highest acquisition indebtedness in the prior 12 months with average adjusted basis, capped at 100%, which is why some investors pay the loan off more than a year before selling. That takes cash the account may not have.

Note what just happened. Depreciation, which is worthless to a tax-exempt account in every other respect, only serves to reduce a tax that exists because the account borrowed.

Solo 401(k) vs SDIRA: why the 401(k) usually wins

For an eligible owner, a solo 401(k) can have an advantage for financed real estate: a qualified plan is generally exempt from UDFI on debt used to acquire real property. The exemption has conditions, including limits on seller financing and on how the price and payments are set, so have the plan's CPA confirm the specific loan fits. An IRA has no such exemption.

Contribution room matters more than it looks. A property in a retirement account can only be fed by the account. If the roof fails and the account holds $3,000 in cash, you cannot write a personal check. You can contribute up to the annual limit, roll in other retirement funds, or sell. The higher limits of a solo 401(k) give the property a bigger safety valve. Check the current year's limits with your plan provider.

The catch is eligibility. You need real self-employment income, and eligible employees, including those who qualify under applicable long-term part-time rules, can end the one-participant treatment. A W-2 employee with a side rental and no business does not qualify, since rental income by itself is not self-employment income.

What you give up: depreciation, 1031s, and cheap loans

This is the part that decides the question for most investors.

Depreciation. Outside an account, a $200,000 structure produces $7,273 of depreciation a year, which shelters rent from tax and, subject to the passive loss rules, can offset other income. Inside an account it shelters nothing, because there is no tax to shelter. You are putting the most tax-advantaged asset class most individuals can own inside a wrapper that ignores its main tax advantage.

Loss deductions. A bad year outside an account generates a passive loss that carries forward. An account loss reduces its assets and does not become a personal Schedule E deduction; account-level tax and carryforward treatment needs separate review.

Capital gains treatment and the 1031 exchange. Outside, a sale is taxed at long-term capital gains rates, with depreciation recapture, and a qualifying 1031 exchange may defer eligible real-property gain. Inside a traditional account, the gain is deferred without any exchange, but every dollar eventually comes out as ordinary income, including appreciation that would have been taxed at capital gains rates. A Roth account avoids that, which is why Roth dollars are the stronger case for this strategy. You also cannot exchange between a personal property and an account-owned one.

Conventional financing. A conventional investor mortgage with 20% to 25% down is unavailable because it requires your guarantee. The non-recourse substitute costs more and demands a larger down payment, which lowers the return on the account's equity. In an IRA it also triggers UDFI.

Your own labor and flexibility. No sweat equity, no living in it later, no renting to family, no covering a shortfall personally.

Liquidity against required distributions. A traditional account eventually faces required minimum distributions. A house cannot be distributed in slices without retitling fractions of it, and the custodian needs a fair market valuation each year, which the account pays for.

Add custodian fees, a separate tax return if there is debt, and the annual valuation, and the wrapper has a real carrying cost before the tenant pays a dollar.

The investor profile this actually fits

The strategy fits a short list of people:

• Most of your investable money is in retirement accounts, and you have little taxable cash to invest.
• You can buy for cash, or nearly so, which sidesteps both non-recourse pricing and UDFI. A solo 401(k) widens this to financed deals.
• The account keeps a large cash cushion after closing, because it is the only source of funds for repairs and vacancies.
• You will hire a third-party manager and keep family away from the property entirely.
• The dollars are Roth, or you accept that traditional dollars convert capital gains into ordinary income on the way out.
• You have a specialist custodian or plan provider and a CPA who files 990-T returns for a living.

If that is not you, the usual answer is to keep index funds in the retirement account and buy the rental with taxable money, where depreciation and conventional debt do their work.

Whichever way you hold it, the property has to stand on its own numbers. Run the deal through the single family calculator with the financing you can get: all cash or non-recourse terms for the account version, conventional terms for the personal version. The wrapper changes the taxes and the loan. It does not change the rent, the roof or the tenant, so a deal that fails ordinary underwriting does not improve inside an IRA.

Next steps: confirm which accounts you are eligible for, get a written non-recourse quote before assuming any debt, price the custodian and tax preparation fees into the operating budget, and have the CPA review the purchase contract before the account signs anything.

This article is general information, not tax advice. Rules change and individual situations differ: confirm anything you plan to act on with a CPA.

A cash-on-cash return calculation measures cash against invested capital; it does not establish which losses are deductible on a tax return.

Use the investor tax tools to organize planning inputs, then reconcile them to the schedules prepared for the return.