Real Estate Tax Calc
Mortgage relief is taxable boot
When you sell a property with a $600,000 mortgage and buy a replacement with only a $400,000 mortgage, you have been relieved of $200,000 in debt. The IRS treats that $200,000 as cash boot received — taxable in the year of the exchange to the extent of your gain. Boot can come from two sources: actual cash you pocket from the exchange, and net debt relief (old debt minus new debt). Both are added together to determine your taxable boot.
You can offset mortgage relief boot by paying additional cash into the replacement. If old debt was $600,000 and new debt is $400,000, putting in an extra $200,000 of your own cash zeroes out the net boot. What you cannot do is the reverse: excess cash invested in the replacement does not create a credit you can apply to cash you receive.
Net boot formula
Net boot = (cash received from sale + old debt assumed by buyer) − (cash paid toward replacement + new debt taken on). If this number is positive, you have taxable boot. Example: sell for $1,000,000 with $400,000 mortgage (equity $600,000), buy for $900,000 with $350,000 mortgage, pay $50,000 additional cash. Net boot = ($0 cash received + $400,000 old debt) − ($50,000 cash paid + $350,000 new debt) = $450,000 − $400,000 = $0. No boot — all the debt relief was covered by additional cash and a small reduction in equity.
If instead you had paid no additional cash and took on only $350,000 in new debt: Net boot = $400,000 − $350,000 = $50,000 taxable.
Practical planning tips
To achieve a fully deferred exchange, ensure you: (1) reinvest all net equity from the sale into the replacement, (2) take on equal or greater debt in the replacement, or (3) compensate for any debt reduction with additional cash. Work with your qualified intermediary early in the process — they can model the boot calculation before you close and identify whether you need to adjust the financing structure of the replacement to avoid an unexpected tax bill.
The two rules that make a fully deferred exchange
Behind the boot arithmetic are two simple requirements for full deferral. First, trade up (or even) in value — the replacement property's price must be equal to or greater than the net sale price of the relinquished property. Second, reinvest all the equity — every dollar of net proceeds from the sale must go into the replacement, none pocketed. If you satisfy both, the debt takes care of itself: matching or exceeding value while reinvesting all equity necessarily means you have replaced the debt or covered any shortfall with cash.
Think of it as replacing both layers of the old property's capital stack. The old property was funded partly by your equity and partly by debt; the replacement must be funded by at least as much of each, with any reduction in one layer made up by adding to the other. New debt can be replaced by new cash, but new cash can never be replaced by new debt you did not actually take on.
Debt can be replaced with cash — but not the reverse
The rule that trips people up is the asymmetry. If your new loan is smaller than your old loan, you can eliminate the resulting debt-relief boot by contributing additional out-of-pocket cash — the cash and the debt reduction offset dollar-for-dollar. But if you take cash out of the exchange, you cannot offset that cash boot by simply borrowing more on the replacement. Cash received is always boot to the extent of gain, full stop.
This is why lenders and qualified intermediaries model the financing before closing. If a replacement property naturally carries a smaller mortgage — say you found a better deal with more equity built in — you either bring cash to fill the gap or accept the boot. Planning the loan amount on the replacement is as much a part of a clean exchange as identifying the property itself.
A worked example with full numbers
Suppose you sell a rental for $800,000 with a $300,000 mortgage, leaving $500,000 of equity (ignore closing costs for clarity). Your qualified intermediary holds the $500,000. You buy a replacement for $900,000. To fully defer, you must apply the entire $500,000 of equity and take on at least $300,000 of new debt — here a $400,000 loan and the $500,000 of equity fund the $900,000 purchase. Net debt: old $300,000 replaced by new $400,000, an increase, so no mortgage-relief boot. All equity reinvested, so no cash boot. Fully deferred.
Now change the replacement to $650,000 financed with a $150,000 loan. You use $500,000 of equity and $150,000 of debt. Old debt $300,000 minus new debt $150,000 = $150,000 of mortgage-relief boot, taxable to the extent of your gain — unless you had instead taken a larger loan or the numbers had forced excess cash back to you (which would also be boot). Trading down in value is the classic way boot sneaks into an otherwise valid exchange.
Where selling costs and financing fees fit
Ordinary transaction costs — brokerage commissions, title fees, transfer taxes, recording fees, and the qualified intermediary's fee — are 'exchange expenses' that reduce your amount realized and generally do not create boot when paid from exchange funds. Loan-related costs on the replacement (points, appraisal, lender fees) are murkier: paying them from exchange proceeds can be treated as receiving boot, because they are costs of obtaining financing rather than costs of the exchange itself. Many advisers have the taxpayer pay financing costs with outside funds to be safe.
Prorated items at closing — property taxes, rent credits, security-deposit transfers — can also inadvertently create small amounts of boot. None of these are usually large, but on a tightly structured exchange they can be the difference between full deferral and a modest taxable amount, so review the settlement statement with your intermediary before closing.
Partial exchanges: choosing how much boot to take
Boot is not always a mistake — sometimes it is a decision. If you need cash out of a property, a partial 1031 exchange lets you defer most of the gain while intentionally recognizing a chosen amount. You might trade down slightly, take a defined amount of cash or debt relief as boot, and pay tax only on that portion while deferring the rest. The key is to do it deliberately: know the gain you are recognizing and confirm you have the cash to pay the resulting tax (including any depreciation recapture, which is recognized first out of boot).
One nuance worth remembering: boot is taxed to the extent of your realized gain, and unrecaptured Section 1250 gain and Section 1245 recapture come out first. So even a modest amount of boot can be taxed at the up-to-25% recapture rate rather than the lower capital-gains rate. If you are going to take boot, run the character of the gain, not just the amount.
Refinancing before or after the exchange
A frequent question is whether you can pull cash out by refinancing rather than taking it as boot. Refinancing the relinquished property right before an exchange is risky: if the refinance is closely tied to the exchange, the IRS can treat the cash you pulled as boot, on the theory that you extracted equity you were supposed to reinvest. There is no bright-line waiting period, but a refinance done for independent reasons, well before any sale is contemplated, is far safer than one executed on the eve of listing.
Refinancing the replacement property after the exchange closes is generally the cleaner route. Once you own the new property free of the exchange, a later cash-out refinance is a borrowing, not a sale — loan proceeds are not taxable income, so you can access equity without triggering gain. Many investors deliberately complete a full, boot-free exchange and then refinance the replacement months later to get tax-free cash in hand. As always, keep the two events genuinely separate and document the business purpose.
Frequently asked questions
What is mortgage relief boot in a 1031 exchange?
It is the taxable amount that arises when you pay off more debt than you take on in the replacement. Reducing your loan balance by $200,000 is treated the same as receiving $200,000 in cash.
What are the two rules for a fully deferred exchange?
Buy a replacement of equal or greater value than the net sale price, and reinvest all of your net equity. Meet both and the debt requirement is satisfied automatically, because you must replace the old debt or make up any shortfall with cash.
Do selling costs create boot?
Ordinary exchange expenses — commissions, title, transfer taxes, and the intermediary's fee — reduce your amount realized and generally do not create boot. Loan-acquisition costs paid from exchange funds can be treated as boot, so many investors pay financing fees with outside cash.
Is a little boot always bad?
No. A partial exchange can be a deliberate way to pull out some cash while deferring most of the gain. Just plan for the tax — boot is taxed to the extent of gain, and depreciation recapture (up to 25%) is recognized before the lower-rate capital gain.
Can I use extra cash to offset mortgage boot?
Yes. If old debt exceeds new debt, you can contribute additional cash to the replacement to eliminate the net debt relief boot. The cash offsets the mortgage reduction dollar-for-dollar.
What if I want to pay off my mortgage entirely in the exchange?
Paying off the old mortgage and buying the replacement free-and-clear creates full mortgage-relief boot equal to the old loan balance, unless you compensate with equivalent cash. This would make the full deferred gain taxable.
Sources
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.