Like-Kind Exchange Boot Explained: How Cash, Debt Relief, and Non-Like-Kind Property Trigger Tax Under Section 1031

You sold your rental property for $600,000, rolled the proceeds into a bigger building across town, and never touched a dime of the cash. The whole point was to defer the tax under Section 1031. Then your CPA calls: you owe tax on $70,000 of gain anyway.

What happened has a name straight out of frontier trading days: boot. Anything in your exchange that is not like-kind property — cash you kept, debt you shed, equipment bundled into the deal — is boot, and the IRS taxes your gain up to the amount of boot you receive. Here is how boot works, the netting rule most exchangers get backwards, and how to keep a partial tax bill from blindsiding you.

What "Boot" Means in a 1031 Exchange​

A like-kind exchange lets you swap real property held for business or investment for other business or investment real property without recognizing gain or loss. The key word is solely: the statute defers tax when like-kind property is exchanged solely for like-kind property.

The moment you receive something else alongside the replacement property, Section 1031(b) requires you to recognize gain — but never more than the value of that something else. That something else is boot. Three rules govern it:

1. Gain recognized is capped at boot received. If you realized $200,000 of gain but received $30,000 of boot, you recognize $30,000 and defer the remaining $170,000.
2. Losses are never recognized. If the exchange is a loss transaction, Section 1031(c) gives you no deduction for the loss, boot or no boot. The loss is buried in the replacement property's basis instead.
3. Deferral is not forgiveness. Gain you defer reduces the basis of your replacement property, so the tax comes due when you eventually sell for cash (unless you exchange again or hold until the basis step-up at death).

Boot comes in three forms, and each one sneaks into exchanges in its own way.

The Three Kinds of Boot​

1. Cash boot​

The simplest kind: money left in your hands at the end of the exchange. Sell for $600,000, buy a $560,000 replacement, and keep $40,000 for renovations — that $40,000 is cash boot, and it is taxable gain to the extent you have gain.

Cash boot does not require a deliberate withdrawal. Prorations settled in your favor at closing, a seller credit you negotiated on the replacement property, or exchange funds released to you because the replacement cost less than expected all count. The IRS does not care why cash stayed with you; it cares that like-kind property did not absorb it.

2. Mortgage boot (debt relief)​

This is the one that surprises people, because no money ever reaches your account. If the mortgage on the property you gave up was larger than the mortgage on the property you received, the difference is debt relief — and debt relief is treated exactly like cash received.

Say your relinquished rental carried a $350,000 mortgage and your replacement property carries only a $320,000 loan. That $30,000 of shed debt is $30,000 of boot, taxable even though you never saw a check. Exchangers who deliberately trade down their leverage — retiring debt as they approach retirement, for example — routinely trigger mortgage boot without realizing it.

3. Non-like-kind property boot​

Anything you receive that is not like-kind real property counts as boot at its fair market value. Since the Tax Cuts and Jobs Act limited Section 1031 to real property (effective January 1, 2018), this category is bigger than many exchangers expect:

• Personal property bundled into the deal — appliances, furniture, equipment, or vehicles conveyed with the real estate — is boot, because personal property no longer qualifies for like-kind treatment at all.
• Foreign real estate received in exchange for U.S. real estate is not like-kind, and vice versa.
• Partnership interests, stocks, bonds, and notes are excluded from like-kind treatment by statute.

A contract that prices the building and its contents as one lump sum is a classic trap: the IRS can reallocate part of your proceeds to the personal property and tax it as boot.

The Netting Rule Most Exchangers Get Backwards​

Here is the rule that saves — or sinks — most partial exchanges: cash you put into the deal offsets mortgage boot you receive, but new debt never offsets cash boot you receive. It works in one direction only.

• Cash offsets debt relief. If you have $50,000 of mortgage boot (shed debt) but bring $50,000 of fresh cash to the replacement closing, the two net to zero. No taxable boot.
• Debt never offsets cash kept. If you pocket $50,000 of proceeds but take on $80,000 of extra debt on the replacement property, you still have $50,000 of taxable cash boot. The additional borrowing does nothing for you.

The practical takeaway: to defer 100% of your gain, you must buy replacement property worth at least as much as what you sold (trade equal or up in value), reinvest all of your equity, and replace all of your debt — topping up any shortfall with cash out of pocket. Miss any one of the three and the shortfall becomes boot.

A Worked Example​

Walk through a realistic exchange to see how the pieces fit:

• Relinquished property: sold for $600,000; adjusted basis $400,000; mortgage $350,000.
• Realized gain: $600,000 − $400,000 = $200,000.
• Replacement property: purchased for $560,000 with a $320,000 mortgage; you keep $40,000 of proceeds.

Now compute the boot:

• Cash boot: $40,000 kept.
• Mortgage boot: $350,000 − $320,000 = $30,000 of debt relief.
• Total boot received: $70,000.

Because your $200,000 realized gain exceeds the $70,000 of boot, you recognize $70,000 of taxable gain this year and defer the remaining $130,000. Had you instead brought $30,000 of cash to closing (wiping out the mortgage boot) and reinvested the full proceeds, the entire $200,000 would have been deferred.

Note what determines the tax character of that recognized gain: it keeps the character it would have had on a straight sale — including any depreciation recapture, which is taxed first out of recognized gain. Boot does not just create a tax bill; it can create one taxed at higher recapture rates.

Five Ways Boot Sneaks Into an Exchange​

Most boot is accidental. Watch for these five:

1. Trading down in value. Buying a cheaper replacement than you sold guarantees leftover proceeds — cash boot — unless you acquire additional replacement property to absorb them.
2. Shrinking your mortgage. Refinancing the replacement with a smaller loan, or buying free and clear with only part of the proceeds, creates mortgage boot for every dollar of debt not replaced.
3. Lump-sum deals with personal property. Farm, restaurant, and short-term-rental sales routinely bundle equipment, furnishings, or vehicles into the price. Each dollar allocated to non-real-property is boot. Get a written allocation in the purchase agreement.
4. Refinancing at the wrong time. Pulling cash out of the relinquished property shortly before the exchange, or out of the replacement shortly after, invites the IRS to recharacterize the loan proceeds as boot. Season any refinance well away from the exchange window.
5. Missing the all-cash-reinvested target by a little. Exchangers sometimes leave a few thousand dollars unspent because the replacement cost slightly less than the sale price. There is no de minimis exception — even a small remainder is fully taxable boot (though only up to your total gain).

Deadlines and Mechanics You Cannot Miss​

Boot only matters if the exchange itself qualifies, and qualification is unforgiving:

• 45-day identification rule. You must identify potential replacement property in writing within 45 days of selling the relinquished property.
• 180-day closing rule. You must receive the replacement property by the earlier of 180 days after the sale or your tax return due date (with extensions) for the year of sale.
• No touching the money. You cannot have actual or constructive receipt of the sale proceeds — not even briefly, not even in escrow. A qualified intermediary must hold the funds between closings. Touch the cash and the exchange collapses into a taxable sale.
• Business or investment use only. Property held primarily for sale (a flipper's inventory) and personal residences do not qualify. Neither does a swap of U.S. property for foreign property.

Miss a deadline or take receipt of the funds and there is no partial credit: the whole sale becomes taxable, boot calculations included.

Reporting Boot: Form 8824 and Your New Basis​

Every like-kind exchange — boot or no boot — gets reported to the IRS on Form 8824, Like-Kind Exchanges, filed with your return for the year you transferred the relinquished property. The form walks through fair market values, mortgages, boot received and paid, realized gain, and recognized gain, and it computes the basis of the property you received.

That replacement basis matters more than most exchangers realize. In broad strokes, your new basis equals your old basis, plus any gain recognized and any cash paid, minus any boot and cash received. Every dollar of boot you are taxed on adds to the replacement property's basis (you already paid tax on it), while every dollar deferred subtracts from it (the tax is still embedded). Sloppy basis tracking here compounds across serial exchanges — investors who 1031 repeatedly without clean records eventually cannot prove their basis at all.

Keep the closing statements from both legs, the exchange agreement, the identification notice, and the Form 8824 workpapers together for as long as you own the replacement property, plus the limitations period after you sell it. The IRS can ask you to substantiate a basis that rolled through three exchanges a decade ago.

Track Every Leg Like Your Deferral Depends on It — Because It Does​

A 1031 exchange is really three accounting problems stapled together: the adjusted basis of what you sold, the boot arithmetic both sides of closing, and the carried-over basis of what you bought. Each one needs its own paper trail — purchase and improvement records for the old basis, settlement statements and loan documents for the boot netting, and a clean opening entry for the replacement property that your future self (and your CPA) can follow without archaeology.

That is a bookkeeping discipline problem as much as a tax problem. If your property records live in a shoebox of PDFs and a spreadsheet last updated two refinances ago, now is the time to fix it: reconstruct the adjusted basis of the relinquished property before you list it, reconcile every dollar of boot at closing, and open the replacement property's books with the computed carryover basis on day one. The Beancount documentation shows how plain-text accounting keeps multi-leg transactions like these explicit and auditable, and the Fava dashboard makes the resulting balances easy to review before your CPA does.

Keep Your Exchange — and Your Books — Clean From Day One​

Boot turns a tax-deferred exchange into a partly taxable one whenever cash, debt relief, or non-like-kind property leaks out of the deal — so identifying it before closing, not after, is what separates a clean deferral from an April surprise. Beancount.io provides plain-text accounting that gives you complete transparency and control over your financial data, so every leg of the exchange stays traceable years later. Get started for free and bring the same rigor to your books that the 1031 rules demand of your exchange.