A partial 1031 exchange is one where you do not reinvest all of the proceeds or all of the value. The part you do not reinvest is called boot, and it is taxable now while the rest of the gain stays deferred. The exchange does not fail. It is just not fully completed, and the tax is calculated on a smaller number rather than the whole gain.

Most people think the 1031 exchange must be an all or nothing thing. Either you roll everything into the replacement property and defer the tax, or you sell outright and pay it.

But that is not how the process works.

An exchange can be partial. You can take cash off the table, or buy something cheaper, or carry less debt than you had, and still defer some or most of the gain. What you keep gets taxed. The gain associated with what you reinvest remains deferred.

That flexibility is useful, and it is also where a lot of exchanges go wrong, because owners create boot without meaning to and do not find out until tax time.

What boot actually is

Boot is anything you receive in the exchange that is not exchanged for like-kind replacement property. In practice it shows up in three ways.

Cash boot. Proceeds that come back to you instead of going into the replacement property. The most obvious version is intentional: you tell the intermediary to send you a cash balance once the transaction has finalized.

Mortgage boot. Debt relief. You had a loan on the property you gave up, and the replacement carries less debt. The difference is treated as though you received it in cash, because in effect somebody paid off your loan and you did not replace the entire obligation. No money touches your hands and it is still taxable.

Trading down in value. Buying a replacement worth less than the one you sold. This is usually one of the other two in a different form, because the shortfall has to come out either as cash or as reduced debt.

The working rule that avoids all three is simple. Buy replacement property of equal or greater value, reinvest all of the net proceeds, and replace the debt with new debt or with your own cash. Miss any of those and you have boot.

The part almost nobody tells you

One rule changes the arithmetic here, and it is the reason a small amount of boot costs more than owners expect.

Boot is not taxed at your capital gains rate. It is characterized first as unrecaptured Section 1250 gain, up to the amount of depreciation you have taken, and only what is left over gets long term capital gain treatment.

For most owners of a property held for years, the depreciation taken is far larger than the boot. Which means the entire boot lands in the 25 percent band before a single dollar reaches the 15 percent band.

So the intuition that taking a little cash out is cheap because capital gains rates are low is wrong. The cash you take out is taxed at the highest rate the sale can produce, first.

How much gets recognized

The rule itself is simple. You recognize gain equal to the lesser of your realized gain or the boot received.

Realized gain is the full gain the sale would have produced if you had not exchanged at all, worked out the same way as any other rental sale. Boot is what you took out.

If your gain is $140,000 and your boot is $20,000, you recognize $20,000. If your gain is $12,000 and your boot is $20,000, you recognize $12,000, because the boot cannot create gain you never had.

Boot also cannot produce a deductible loss. If the property sold at a loss, an exchange is usually the wrong structure anyway, and that is a conversation to have before you engage an intermediary rather than after. The rules described above are the general shape of how boot is treated. Your own outcome depends on your basis, your depreciation history, the debt on both properties, how the closings are structured, your income in the year of the exchange, and your state.

Working through an actual number

The figures below are illustrative.

Take the same rental used in the article on capital gains. Bought twelve years ago for $187,500 with a $150,000 loan, sold for $300,000, and carrying about $112,000 of remaining debt. Selling costs run 8 percent, and twelve years of depreciation come to $65,455.

Where the exchange starts

  • Sale price: $300,000
  • Minus selling costs: $24,000
  • Minus loan payoff: $112,000
  • Net proceeds held by the intermediary: $164,000
  • Realized gain, calculated the ordinary way: $141,955

The replacement

The owner buys a replacement for $280,000 with a new loan of $136,000, which needs $144,000 of cash at closing.

That leaves $20,000 of the $164,000 unspent, and it comes back to the owner. Debt went up rather than down, from about $112,000 to $136,000, so there is no mortgage boot.

  • Cash boot: $20,000

The tax on it

  • Recognized gain, the lesser of $141,955 and $20,000: $20,000
  • Depreciation taken was $65,455, which is more than the boot, so all $20,000 is unrecaptured Section 1250 gain
  • At up to 25 percent: $5,000
  • Net investment income tax at 3.8 percent, if the owner is over the threshold: $760

What it compares to

At the long term capital gains rate of 15 percent, that $20,000 would have cost $3,000. It costs $5,000, because of the ordering rule in the above example.

And a straight taxable sale of the same property would have produced a federal bill of about $27,839. So the partial exchange defers $121,955 of gain and costs roughly $5,000 to $5,760 now, in exchange for taking $20,000 in cash.

Whether that is a good trade depends entirely on what the $20,000 is for. Paying $5,000 to free $20,000 you need is a defensible move. Paying $5,000 because $20,000 was left over by accident is not.

The deferred gain does not disappear

One more important thing follows from the example, and owners consistently miss it.

Your basis in the replacement property is not what you paid for it. It is reduced by the gain you deferred. In the example above, a $280,000 replacement with $121,955 of deferred gain carries a basis of about $158,045.

That has a cost you feel every year. Depreciation on the replacement is calculated from the lower figure, not from the purchase price, so the annual deduction is smaller than it would be for a buyer who paid the same $280,000 in an ordinary purchase.

The deferral is real and a 1031 Exchange is worth considering. But it also should not be considered free, as the cost of that deferral shows up on the depreciation schedule for as long as you own the replacement due to the lower basis you can report.

Three ways owners create boot without meaning to

The deliberate version is easy to understand. You wanted cash out or a lower mortgage. These are the ones that surprise people.

Debt goes down and nothing replaces it. You had a $200,000 loan and the replacement only needs $150,000. That $50,000 of relief is boot unless you put $50,000 of your own outside cash into the deal. Consolidating into a property you can buy with less leverage is one of the most common ways this happens, and it is exactly the case the article on exchanging several properties into one flags.

Money is left over at the end. The replacement came in cheaper than planned, or the seller credited something at closing, and there is a balance sitting with the intermediary. It gets released to you and it is boot.

Non-qualifying costs get paid out of exchange funds. Ordinary transaction costs such as commissions and intermediary fees generally come out of proceeds without creating a problem. Other items commonly settled at closing, including prorated rents, security deposits transferred, and some tax and utility prorations, can be treated differently. This is detail your intermediary and your CPA handle together, and it is worth asking about before closing rather than after.

None of these can be fixed afterwards. Once the exchange closes, the numbers are the numbers.

When a partial exchange is the right answer

There is a version of this that is not a mistake at all.

Sometimes you need the cash. A partial exchange lets you take what you need, pay tax on that piece only, and defer everything else. Compare that to the alternatives. A full taxable sale taxes the whole gain. A full exchange defers everything and leaves you with no cash. This partial version rests between them, and for an owner who needs a specific amount for a specific reason, it is often the cleanest structure available.

It also beats the thing owners do instead, which is stretch to buy a replacement they do not want purely to avoid boot. Paying $5,000 of tax is usually a smaller mistake than buying the wrong property for $280,000 under a 45 day deadline.

The deadlines still apply in full. A partial exchange is a normal deferred exchange with an incomplete reinvestment, so the 45 day identification window and the 180 day completion window run exactly as they would otherwise, and the intermediary still has to be engaged before the relinquished property closes. Work the numbers with your CPA and your qualified intermediary before you commit to a replacement property or a closing date.

The question underneath all of this

The tax arithmetic tells you what a partial exchange costs. It does not tell you whether to do one.

That comes down to what you are trying to accomplish. An exchange, partial or full, keeps capital working and hands you a real deadline. A taxable sale costs you the gain and the recapture and leaves you free to buy nothing, buy something later, or buy something better. Both change the income, the leverage, and the concentration across everything you own.

The comparison worth running is not a partial 1031 exchange against a full exchange. It is all three paths, full exchange, partial exchange, and taxable sale, measured against what the portfolio is supposed to do and against simply keeping the property.

A qualified intermediary's job is to make the exchange work mechanically. Deciding whether it should happen is a separate job, and nobody in the transaction is paid to make that decision for you.

Novarif is being built to show rental property owners what an exchange does to the whole portfolio, and to compare a full exchange, a partial exchange, and a taxable sale side by side against income, coverage, equity, and the goal. Join early access to run the comparison before you commit.