Form 8824: Calculating Realized vs Recognized Gain on a 1031 Exchange

A 1031 exchange lets you defer—or avoid entirely—capital gains tax when you sell one investment property and buy a similar one, but only if you properly calculate realized gain, recognized gain, and the basis of your replacement property. Form 8824 is where you make those calculations and prove the exchange qualified for deferral.

What makes gain “realized” and what makes it “recognized”

Your realized gain is straightforward arithmetic: the sales price of the relinquished property, minus your adjusted basis. If you bought a rental building for $500,000 and sold it for $750,000, your realized gain is $250,000. That number doesn’t change based on tax law—it’s the economic reality.

Your recognized gain is the portion the IRS forces you to pay tax on in the current year. In a perfect 1031 exchange, you recognize zero gain and defer the entire $250,000. But if you receive boot—cash, a mortgage payoff, or any property that isn’t like-kind—you must recognize gain up to the boot amount. If your buyer pays off $100,000 of your loan and gives you $50,000 in cash, you’ve received $150,000 in boot and must recognize gain of $150,000 (or your realized gain, whichever is smaller).

Form 8824 Part II walks through this: starting with realized gain, subtracting deferred gain, and arriving at recognized gain. The difference is deferred—it rolls into the basis of your replacement property rather than triggering a tax bill today.

How basis carries forward to the replacement property

The basis of your replacement property is not its purchase price. Instead, it’s built from what you deferred.

Start with the adjusted basis of the property you gave up. Add any boot you paid (cash you sent, debt you assumed on the replacement property). Subtract any boot you received. Add any gain you recognized. The result is your new basis.

Example: You sell a property with $500,000 basis for $750,000. You receive $100,000 boot. Your realized gain is $250,000, and you recognize gain equal to the boot ($100,000). Your basis in the replacement property is: $500,000 (old basis) + $100,000 (boot paid, if any) – $100,000 (boot received) + $100,000 (gain recognized) = $600,000. That $600,000 basis preserves the $150,000 of deferred gain—when you eventually sell the replacement property, that gain will resurface.

This is why Form 8824 Part III exists: it documents every component so your basis calculation survives audit. Many taxpayers gloss over this and arrive at the wrong starting point for future depreciation, putting themselves at risk years later.

Boot and why it triggers recognition

Boot comes in three flavors: cash received, net debt relief, and unlike property. Each triggers gain recognition dollar-for-dollar, capped at your realized gain.

Cash is obvious. You sell a property, buyer hands you $50,000 in cash, you recognize up to $50,000 of your realized gain.

Debt relief is trickier but equally taxable. If you owe $300,000 on the relinquished property and your buyer assumes $280,000 (leaving you $20,000 liability on the replacement), you’ve netted $20,000 from the exchange—that’s boot, even though no cash changed hands. This net debt relief is the most commonly missed boot amount.

Unlike property—a car, equipment, cryptocurrency, securities—also counts as boot and must be reported at fair value. A true 1031 only defers gain if you swap real estate for real estate. Any deviation triggers recognition.

Form 8824 Part I asks specifically about boot received in two categories: cash and other property. Part II then plugs these into the recognized-gain calculation. Many exchanges claim zero boot when debt relief was present, which draws auditor attention.

Timing, identification windows, and when Form 8824 is due

You must identify replacement property within 45 days and close on it within 180 days (or by the tax-return deadline, whichever is earlier). Form 8824 goes on the return for the year you completed the exchange.

One common trap: if your replacement property purchase extends into the next calendar year (say, you sell in December but don’t close until February), the form goes on your return for the year of the sale, not the year of purchase. The 180-day clock runs from the date you sold the relinquished property, regardless of when you file.

If you’re swapping multiple properties or the exchange is complex, you’ll file Form 8824 for each leg. A simultaneous exchange (you sell A and buy B in one transaction) and a delayed exchange (sell A in year one, buy B in year two, but within the 180-day window) are both reported on the 8824 for the sale year.

Distinguishing related-party exchanges and equal-or-greater-value requirements

A 1031 works only if your replacement property is of equal or greater value than what you sold. If you sell a $500,000 building and buy a $400,000 one, you’ve received $100,000 in boot (the unexchanged proceeds), and that forces gain recognition.

Related-party exchanges have extra teeth: if you sell to or buy from a spouse, sibling, or business partner, the exchange is permitted, but if either party disposes of their property within two years, the original deferral is clawed back and you owe the tax retroactively. This is one of the nastiest surprises in the tax code and rarely explained at the point of sale. Form 8824 Part IV is where you flag a related-party exchange.

Common mistakes that invite audit or penalty

Claiming zero boot when you had net debt relief is the most frequent mistake. Undervaluing unlike property you received is another. Buying personal-use property instead of pure investment property (you can exchange a rental home for another rental, but not for a vacation home) also blows the deferral.

Incorrectly calculating the basis of the replacement property leads to wrong depreciation deductions for years afterward, triggering correspondence years later. Getting the replacement-property basis right on Form 8824 Part III is worth the time to verify.

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