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The 1031 Exchange: Deferring Gain, and Why 2026 Makes It Even More Powerful

 

A 1031 exchange lets you sell investment or business real estate, roll the proceeds into another property, and defer the capital gains tax, potentially indefinitely. It's one of the oldest tools in real estate tax planning, and it just got a lot more interesting thanks to the same 2025 law change that supercharged cost segregation studies.

 

Here's how the mechanics actually work, where people get tripped up, and why pairing a 1031 exchange with a cost segregation study on the replacement property has become one of the more powerful combinations available to real estate investors right now.

 

The Basic Mechanics

 

Section 1031 allows a taxpayer to defer capital gains tax, depreciation recapture, and the net investment income tax on the sale of real property held for investment or business use, as long as the proceeds are reinvested into "like-kind" replacement real property. Since 2018, this only applies to real property — personal property (equipment, vehicles, and similar assets) no longer qualifies for 1031 treatment at all, which matters for the cost segregation interaction discussed below.

 

The core requirements:

 

• A qualified intermediary is required. You can't touch the sale proceeds directly - they need to be held by a qualified intermediary between the sale of the relinquished property and the purchase of the replacement property. Taking possession of the funds, even briefly, disqualifies the exchange.

 

• 45-day identification window. From the date the relinquished property closes, you have 45 calendar days to formally identify potential replacement properties, in writing, to the qualified intermediary.

 

• 180-day closing window. You then have 180 calendar days total (not in addition to the 45) from the original closing to complete the purchase of the replacement property.

 

These deadlines are strict and calendar-day based - no extensions for weekends, holidays, or difficulty finding a suitable replacement property. Missing either one collapses the entire exchange and triggers the tax bill in full.

 

"Like-Kind" Is Broader Than People Think

 

Despite the name, "like-kind" for real estate is interpreted quite broadly - essentially any real property held for investment or business use can be exchanged for any other real property held for the same purpose. An apartment building can be exchanged for raw land, a retail strip mall for an industrial warehouse, and so on. The restriction is about the nature of the property (investment/business real estate) rather than requiring similar property types.

 

Avoiding "Boot"

 

To defer 100% of the gain, the replacement property generally needs to be of equal or greater value than the relinquished property, and all of the net proceeds need to be reinvested. Any cash or non-like-kind property received in the exchange,  called "boot" is taxable to the extent of gain realized, even within an otherwise valid exchange. Reducing debt on the replacement property relative to the relinquished property can also create boot, since a debt reduction is treated similarly to receiving cash. This is one of the more common ways an exchange ends up partially taxable without the investor realizing it going in.

 

The Big 2026 Wrinkle: Pairing 1031 With Cost Segregation

 

This is where things have gotten genuinely more interesting. As covered in more detail in our post on cost segregation, the One Big Beautiful Bill Act permanently restored 100% bonus depreciation for qualifying property, and that interacts with 1031 exchanges in a specific and valuable way.

 

A common misconception is that depreciation resets, or that accelerated depreciation isn't available at all, on a property acquired through a 1031 exchange. In reality, cost segregation and bonus depreciation remain fully available on the replacement property - it just requires understanding how the basis splits.

 

Under the applicable Treasury regulations, a replacement property acquired through a 1031 exchange has its basis divided into two distinct pieces, treated differently for depreciation purposes:

 

• Carryover (exchanged) basis — this is the basis from the relinquished property, carried forward into the replacement property. It generally continues on the same depreciation schedule and remaining recovery period it was already on, and is not eligible for new bonus depreciation.

 

• Excess basis — this is any additional money, whether cash or new debt, used to acquire a replacement property worth more than the relinquished one. This portion is treated as newly placed-in-service property, on a fresh depreciation schedule, and is fully eligible for cost segregation and 100% bonus depreciation.

 

In practical terms: the more "new money" (cash or new financing) an investor brings to the replacement property purchase, the larger the excess basis — and the larger the immediate, first-year deduction available through a cost segregation study performed on that excess basis. An investor upgrading from a smaller, largely depreciated property into a substantially larger one, especially with meaningful additional financing, can generate a very large first-year deduction on top of the capital gains they've already deferred.

 

A simplified illustration: a property sells for $1 million in a 1031 exchange, with $700,000 of remaining carryover basis. The investor acquires a $1.5 million replacement property. Only the $500,000 of excess basis (the difference between the replacement property's cost and the relinquished property's basis) is eligible for bonus depreciation through cost segregation — the $700,000 carryover basis continues on its original schedule.

 

Timing matters here too. Ideally, the cost segregation study on the replacement property is done in the same tax year the exchange closes, so the full first-year bonus depreciation benefit is captured immediately rather than delayed. If a study wasn't done at the time, a look-back study combined with a Form 3115 accounting method change can still catch up the missed depreciation later, though this loses some of the time-value benefit of claiming it in year one.

 

A Recapture Wrinkle Worth Knowing

 

Cost segregation on a 1031 replacement property increases the amount of the building reclassified as Section 1245 property (the shorter-life personal-property-type components), rather than Section 1250 property (the building structure itself). This matters because a 1031 exchange doesn't automatically defer Section 1245 recapture the way it defers Section 1250 recapture - full deferral of the Section 1245 portion generally requires that the next replacement property include enough Section 1245-type property to fully offset it. This is a technical point, but it's exactly the kind of detail that needs modeling before an investor assumes a future exchange will defer everything the way a prior, simpler exchange did.

 

State Conformity, Again

 

As with bonus depreciation generally, not every state conforms fully to federal 1031 exchange or bonus depreciation treatment — several states have moved to "decouple" from parts of the federal bonus depreciation rules specifically to preserve state revenue. An investor modeling the combined benefit of a 1031 exchange plus cost segregation needs to check state-level treatment separately, rather than assuming the full federal benefit carries through everywhere.

 

Other Considerations Worth Flagging

 

• DSTs (Delaware Statutory Trusts) are sometimes used as 1031 replacement property for investors who want to exit active property management while remaining in a like-kind structure — worth exploring if hands-on ownership isn't the goal going forward.

 

• Reverse exchanges, where the replacement property is acquired before the relinquished property is sold, are possible but more complex and costly to structure, generally requiring an exchange accommodation titleholder to hold one of the properties temporarily.

 

• A 1031 exchange can be repeated indefinitely across an investor's lifetime, deferring gain from one property into the next. Combined with the basis step-up available at death, gain that's been deferred through a series of exchanges can, in the right circumstances, ultimately avoid capital gains tax altogether for the investor's heirs — though estate size and current estate tax exemption levels are a separate analysis worth having with a tax advisor.

 

The Bottom Line

 

A 1031 exchange remains one of the most effective tools for deferring and, with the right long-term planning, potentially permanently avoiding capital gains tax on real estate. What's changed is that pairing it with a cost segregation study on the replacement property, now backed by permanent 100% bonus depreciation, can generate a substantial first-year deduction on top of the deferred gain, particularly for investors bringing meaningful new capital or financing into a larger replacement property. Getting the basis allocation and timing right takes coordination between the qualified intermediary, the cost segregation firm, and your tax advisor, not something to piece together after the fact.