What Is Boot in a 1031 Exchange? Cash Boot, Mortgage Boot, and Fresh-Cash Offsets

A 1031 exchange is supposed to defer your gain in full. Most of the time, it does. The cases where an investor gets a surprise tax bill almost always come down to one word: boot. You did a real exchange, you used a qualified intermediary, you hit your deadlines, and you still owe tax on part of the deal. That part is the boot.

Boot is the piece of the trade that is not like-kind property. In a like-kind exchange under Section 1031, only the real estate you roll into replacement property gets deferral. Anything else you walk away with, cash, debt relief, or non-like-kind property, is boot, and boot is taxable up to the amount of your gain.

There are two kinds that come up in real estate deals, and they behave differently. One of them is symmetrical. The other is not, and the asymmetry is where people get tripped up. You can run any of this through the 1031 exchange calculator to see the exact taxable number before you sign anything, and the Partial Exchange preset below walks through the most common version of the problem.

What boot actually is

Boot is value you receive in the exchange that is not replacement real estate. Two flavors matter here.

Cash boot is money you pocket. If you do not reinvest all of your net proceeds into the replacement property, the leftover cash is boot. It does not matter that the rest of the deal was a clean exchange. The cash you kept is taxable.

Mortgage boot is debt relief. If the loan on your new property is smaller than the loan you paid off on the old one, you came out of the deal owing less than you did going in. The IRS treats that drop in debt as if you received cash, because in effect you did. That net reduction in liabilities is mortgage boot.

The general rule for full deferral is simple to state: buy equal or up in value, and replace your debt with equal or more debt (or with your own cash). Fall short on either, and the shortfall is boot.

How cash boot works

Cash boot is the easy one to understand and the hardest one to undo once it happens.

When you sell, your net proceeds sit with the qualified intermediary. You never touch them. To get full deferral, you have to spend all of that cash on the replacement property. Whatever the QI does not need to close the purchase comes back to you, and that returned amount is cash boot.

Take the Partial Exchange scenario. You sell for $1,000,000 with $50,000 in exchange costs, so your net amount realized is $950,000. Your old loan is $300,000, which means the QI is holding $650,000 in cash for you ($950,000 net proceeds minus the $300,000 that paid off the old loan).

Your replacement property costs $900,000 and you put a $300,000 loan on it. So the cash you actually need to close is $600,000 ($900,000 price minus the $300,000 new loan). The QI hands $600,000 to the closing, and the remaining $50,000 goes back to you.

That $50,000 is cash boot. You did not reinvest it, so it is taxable. Debt stayed flat at $300,000, so there is no mortgage boot in this deal. The only boot is the cash you pocketed.

How mortgage boot works

Mortgage boot is about the loans, not the cash. Compare the debt you were relieved of against the debt you took on.

If your old loan was $400,000 and your new loan is $300,000, you walked away $100,000 lighter on debt. On its own, that $100,000 of net debt relief looks like mortgage boot, and the IRS would tax it the same way it taxes cash you kept.

The reason mortgage boot exists is that paying off the old loan freed you from a liability. Economically that is a benefit, the same as if someone had handed you $100,000 to settle the loan. So the tax code counts it.

Here is the part that saves a lot of deals. Mortgage boot can be offset.

Why fresh cash can offset mortgage boot

You are allowed to plug a debt gap with your own money. If your new loan is smaller than your old one, you can bring outside cash to the closing to make up the difference, and that cash cancels the mortgage boot.

This is the strongest example, so look at the numbers closely. You sell for $1,000,000 with $50,000 in costs, net amount realized $950,000. Your old loan is $400,000, so the QI holds $550,000 in cash ($950,000 minus the $400,000 payoff).

Your replacement costs $950,000 and you put a $300,000 loan on it. The cash needed to close is $650,000 ($950,000 price minus the $300,000 loan). But the QI only has $550,000. You are short by $100,000.

So you bring $100,000 of your own money to the table. That fresh outside cash covers the gap, and here is the key: it also offsets the $100,000 of debt relief. The new loan is $100,000 smaller than the old loan, which by itself would be mortgage boot, but you replaced that missing $100,000 of debt with $100,000 of your own cash. Net taxable boot is $0. Recognized gain is $0. The full $700,000 of realized gain stays deferred.

This is why “buy down on debt” does not automatically trigger tax. A smaller mortgage is fine as long as you fill the hole with equity.

The asymmetry that catches people

Now the part that surprises investors. The offset works in one direction only.

Fresh outside cash can offset a smaller new mortgage. A bigger new mortgage cannot offset cash you already took out of the deal.

Put the two examples side by side. In the mortgage-boot case, bringing $100,000 of cash erased $100,000 of debt relief, because you put more value into the deal than you took out. That direction works.

But it does not run the other way. In the cash-boot case, suppose you tried to fix your $50,000 of cash boot by taking on a larger loan on the replacement property. It does not help. You already pocketed the $50,000. Once that cash is in your hands and out of the exchange, borrowing more on the new property does not pull it back in. A bigger mortgage adds debt; it does not un-receive cash you have already received.

The rule underneath this is what makes the calculator’s numbers behave the way they do. Cash boot is value leaving the exchange to you. Mortgage boot offset by fresh cash is value you are adding back in. You can always add value back to cure a shortfall. You cannot retroactively cure cash you already removed by piling on debt somewhere else.

How recognized gain is capped

One more rule keeps boot from ever overstating your tax. Recognized gain can never exceed realized gain.

Realized gain is your full economic gain on the sale, whether or not any of it is taxed this year. Recognized gain is the slice that actually gets taxed. Boot determines how much of the realized gain is recognized, but it can never push recognized gain above the realized number.

In the Partial Exchange scenario, your adjusted basis is $275,000 (original basis of $350,000 minus $75,000 of depreciation), and your net amount realized is $950,000, so your realized gain is $675,000. Your boot is $50,000. Recognized gain is the lesser of the boot and the realized gain, which is $50,000. The other $625,000 of gain stays deferred.

What does that $50,000 of recognized gain cost in tax? With $180,000 of other income as a single filer, the boot is taxed first as unrecaptured Section 1250 gain, $12,282.25, plus the 3.8% net investment income tax of $1,140. That rounds to $13,422 of tax on the boot. You deferred the remaining $625,000.

In the mortgage-boot example, realized gain is $700,000 (net amount realized of $950,000 minus an adjusted basis of $250,000, which is the $300,000 original basis less $50,000 of depreciation). Because the fresh cash zeroed out the boot, recognized gain is $0 and all $700,000 stays deferred. Same kind of deal, very different tax outcome, and the difference is entirely about how you handled the cash and the debt.

What to do with this

Before you close on a replacement property, run the two levers, cash and debt, against your sale. Reinvest all of your net proceeds, and replace your old debt with equal or greater debt or with your own equity. If you do both, boot is zero and your gain defers in full.

If you know you want to pull some cash out, fine, but go in knowing it is taxable and model the number first. And if you are buying down on your mortgage, remember you can offset that with fresh cash, but you cannot use a bigger mortgage to wash out cash you already took. Plug your own figures into the Partial Exchange preset in the 1031 exchange calculator and you will see exactly where your taxable boot lands before you are committed.

Sources

IRS, Like-Kind Exchanges, Real Estate Tax Tips
IRS, Instructions for Form 8824
IRS, Publication 544

Frequently Asked Questions

What is boot in a 1031 exchange?

Boot is any value you receive in the exchange that is not like-kind replacement real estate. The two common kinds are cash boot, which is proceeds you do not reinvest, and mortgage boot, which is net debt relief when your new loan is smaller than your old one. Boot is taxable up to the amount of your gain, even when the rest of the exchange is clean.

What is the difference between cash boot and mortgage boot?

Cash boot is money you pocket because you did not spend all of your net proceeds on the replacement property. Mortgage boot is the drop in your debt when the loan on the new property is smaller than the loan you paid off on the old one. Cash boot is value leaving the exchange to you. Mortgage boot is a liability you no longer carry, which the IRS treats as if you received cash.

Can fresh cash offset mortgage boot?

Yes. If your new loan is smaller than your old one, you can bring outside cash to the closing to cover the difference, and that cash cancels the mortgage boot. In the example above, a $100,000 buy-down on debt was fully offset by bringing $100,000 of the investor’s own money to close, which dropped net taxable boot to $0.

Can a bigger mortgage shelter cash boot?

No. The offset only runs one way. Fresh cash can cancel a smaller new mortgage, but taking on a larger mortgage cannot wash out cash you already took out of the deal. Once you have pocketed the cash, it is received, and borrowing more on the replacement property does not un-receive it.

How is the tax on boot calculated?

Your recognized gain equals the boot, capped at your realized gain, since recognized gain can never exceed realized gain. That recognized amount is then taxed according to its character. In the Partial Exchange scenario, $50,000 of cash boot was taxed as unrecaptured Section 1250 gain ($12,282.25) plus 3.8% net investment income tax ($1,140), for $13,422 of tax, while the remaining $625,000 of gain stayed deferred.