Boot in a 1031 Exchange: What Is Taxable

In a 1031 exchange, boot is any cash or non-real-estate property that the seller receives without reinvesting it back into replacement real estate. Any boot received is immediately taxable as a capital gain, even though the rest of the exchange qualifies for tax deferral. Understanding boot—both cash boot and mortgage boot—is essential to structuring exchanges that fully defer taxes.

The core rule: reinvestment avoidance triggers tax

The Internal Revenue Code Section 1031 allows a taxpayer to exchange real property held for investment or business use for other real property of like-kind, with tax deferral on the capital gain. The deferral works because the taxpayer has not “cashed out” the investment—they simply swapped one property for another.

Boot—any value the taxpayer pockets instead of reinvesting—breaks that logic. If you sell a property for $500,000 and buy a replacement for $400,000, keeping the $100,000 difference in cash, you have partly cashed out. That $100,000 is taxable. The IRS treats boot as equivalent to a partial sale and applies capital gains tax to it immediately, even though the exchange of the remaining value qualifies for deferral.

Boot can take two forms: cash boot and debt boot (or mortgage boot). Both are taxable if received.

Cash boot: the straightforward case

Cash boot is the simplest form. It arises when the replacement property costs less than the relinquished property, or when the seller accepts cash as part of the exchange instead of taking a replacement property of equal value.

Example: Under-funded replacement

Sarah owns an apartment building with a value of $800,000 and a cost basis of $300,000. She sells it and purchases a replacement property for $650,000. The difference, $150,000, is her cash boot.

Because she received $150,000 in cash that she did not reinvest in real estate, that $150,000 is immediately taxable as a long-term capital gain (assuming she held the original property more than one year). Her realized gain is $500,000 ($800,000 sale price minus $300,000 basis), but $150,000 of that is recognized as taxable income. The remaining $350,000 gain is deferred.

If Sarah is in a 20% long-term capital gains tax bracket, she owes $30,000 in tax on the $150,000 boot, even though the transaction is nominally a 1031 exchange.

The equal-or-greater-value rule

To avoid cash boot altogether, the replacement property must be equal to or greater in value than the relinquished property. Many 1031 exchangers follow this principle: “exchange up or equal.” Buy a more expensive property or one of equivalent price; never buy down.

Mortgage boot: the hidden tax trap

Mortgage boot (or debt boot) is more subtle and often misunderstood. It arises from changes in the amount of debt secured by the properties in the exchange.

How mortgage boot is calculated

In a 1031 exchange, if the debt on the relinquished property exceeds the debt on the replacement property, the difference is boot.

Example: Debt reduction triggers boot

Marcus owns a rental building worth $1,000,000 with a mortgage of $600,000. His equity is $400,000. He exchanges it for a new rental property worth $1,000,000 with a mortgage of $500,000.

His relinquished property: Debt $600,000 His replacement property: Debt $500,000 Debt relief: $600,000 − $500,000 = $100,000

That $100,000 debt relief is treated as boot received. Marcus is deemed to have received $100,000 in cash benefit (because he owes $100,000 less on the replacement property), so $100,000 is taxable.

Why the IRS treats debt relief as boot

The rationale is economic equivalence. If Marcus had sold the building outright, the lender would release the $600,000 lien. He could then use the proceeds to pay off $500,000 of the new mortgage, keeping the $100,000 difference. The IRS takes the view that debt relief in an exchange is the same as receiving cash and using it to pay down debt; either way, Marcus benefits from $100,000 in value without reinvesting it in new equity.

Combining cash and mortgage boot

In more complex exchanges, both types of boot can appear.

Example: Multiple adjustments

Jennifer owns a commercial building worth $1,200,000 with a mortgage of $700,000. She sells and receives $500,000 in cash (after the lender is paid from sale proceeds). She purchases a replacement property worth $1,100,000 and finances it with an $800,000 mortgage.

Her situation:

• Relinquished debt: $700,000
• Replacement debt: $800,000
• Debt change: No debt relief; she actually increased debt. No mortgage boot.
• Cash received: She keeps $500,000 in cash instead of using it to reduce her new mortgage.
• Taxable boot: $500,000 in cash boot.

Her realized gain is $500,000 ($1,200,000 sale price minus $700,000 cost basis). She receives $500,000 in taxable boot, so her entire gain is recognized in the year of exchange.

The role of intermediaries in boot calculation

A third-party qualified intermediary facilitates most 1031 exchanges and helps the exchangor navigate boot rules. The intermediary must hold the sale proceeds in trust and redirect them toward the replacement property purchase within strict timelines (45 days to identify, 180 days to close).

If the exchangor takes possession of sale proceeds themselves, even briefly, the entire transaction may be disqualified as a 1031 exchange and the full gain becomes immediately taxable. This is why intermediaries are essential: they ensure the exchangor never touches the cash, preventing accidental cash boot.

That said, if the replacement property costs less than the relinquished property, the intermediary will eventually return the shortfall to the exchangor. That returned cash is still boot.

Boot and basis adjustments

When boot is involved, the exchangor’s cost basis in the replacement property is adjusted. This is not an escape clause; it is a deferral of the tax, not an elimination.

Example: Basis carryover with boot

David exchanges a property with a basis of $300,000 and fair market value of $500,000 for a replacement property worth $500,000. He receives no boot. His basis in the replacement property becomes $300,000 (the original basis carries over). If he later sells the replacement property for $550,000, he realizes a $250,000 gain ($550,000 sale price minus $300,000 basis).

By contrast, if David had received $50,000 in cash boot, his basis in the replacement property is $250,000 (original basis of $300,000, reduced by the $50,000 boot recognized as a gain). He has paid capital gains tax on the $50,000 boot at the time of exchange, so that amount does not inflate his basis.

Timing and tax planning

The boot tax is owed in the year the exchange closes. If an exchangor knows they will receive boot, they should plan for the tax liability before the exchange concludes. Some exchangors structure deals to reinvest sufficient proceeds in the replacement property (buying up in value) to avoid or minimize boot, or they plan to pay the tax from other sources and avoid a shortfall.

In some cases, an exchangor deliberately takes boot as part of a tax strategy. If they expect a large deferred gain but need liquidity, accepting boot allows them to realize some of the gain (and pay tax on it) while deferring the rest. This is useful when a large deferred gain would create bunching in a single year at a higher tax rate than spreading recognition over two years.

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