By Income Tax Service Editorial — Reviewed by Diyan Yap, EA (IRS Enrolled Agent) — Updated August 10, 2026
Quick answer: A cost segregation study breaks a purchased building into its components and reclassifies the 5-, 7-, and 15-year items out of the 27.5-year residential or 39-year nonresidential schedule. Those short-life components then qualify for 100% first-year bonus depreciation, which OBBBA restored permanently for property acquired and placed in service after January 19, 2025.
Key facts:
- Reclassifies fixtures, specialty electrical, carpet, parking, and landscaping into 5-, 7-, and 15-year property
- Short-life components qualify for 100% first-year bonus depreciation (permanent under OBBBA)
- Bonus applies to property acquired and placed in service after January 19, 2025 (January 1–19, 2025 property falls under the old 40% rate)
- The building shell itself never qualifies for bonus depreciation
- Illustration from IRS-sourced guidance: a $1,000,000 building with $250,000 of short-life components yields a $250,000 year-one deduction versus roughly $36,000 on a straight-line schedule
Cost segregation is not a loophole and not new — it is an engineering-based allocation of purchase price that the tax code has always contemplated. What changed is the payoff: with 100% bonus depreciation permanent again, every dollar moved into a short-life class becomes a first-year deduction rather than a slow drip.
What is a cost segregation study?
A cost segregation study is an engineering and accounting analysis that splits a building’s purchase price into its actual components. Instead of treating an entire acquisition as one long-lived asset, the study identifies the pieces that tax law already assigns shorter recovery periods — carpet, cabinetry and fixtures, specialty electrical serving equipment, parking areas, sidewalks, and landscaping.
Without a study, a buyer typically depreciates the whole improved value over 27.5 years (residential rental) or 39 years (nonresidential). With a study, the short-life slices come out of that schedule and onto their own, much faster ones.
The land under the building is never depreciable, and the structural shell stays on the long schedule. A study does not invent deductions — it documents the classification of dollars you already spent.
| Component class | Typical items | Recovery period | Eligible for 100% bonus |
|---|---|---|---|
| 5-year property | Carpet, cabinetry, decorative fixtures, specialty electrical | 5 years | Yes |
| 7-year property | Certain equipment and furnishings | 7 years | Yes |
| 15-year land improvements | Parking lots, sidewalks, landscaping, site utilities | 15 years | Yes |
| Residential structure | The building shell of a rental property | 27.5 years | No |
| Nonresidential structure | The building shell of commercial property | 39 years | No |
How does cost segregation unlock 100% bonus depreciation?
It works because bonus depreciation is available to property with a recovery period of 20 years or less — and the building itself isn’t. OBBBA restored 100% first-year bonus depreciation permanently for qualified property acquired and placed in service after January 19, 2025, which means a component moved into the 5-, 7-, or 15-year classes can be fully deducted in the first year rather than spread across decades.
That is the whole mechanism: the study changes the class, and the class determines whether bonus applies. Qualified improvement property and used property bought in an arm’s-length purchase can also qualify, which is why cost segregation matters on acquisitions of existing buildings, not just new construction.
The order of operations matters too. Property acquired and placed in service between January 1 and January 19, 2025 falls under the older 40% bonus rate, so early-2025 purchases need their dates checked before anyone projects a first-year number. Our 100% bonus depreciation guide covers the eligibility rules in detail.
What does a cost segregation study actually save? (worked example)
Consider a $1,000,000 building where a study identifies $250,000 of 5-, 7-, and 15-year components:
- Without a study: the full improved value stays on the long schedule, producing roughly $36,000 of first-year depreciation
- With a study: $250,000 of components move to short-life classes and qualify for 100% bonus depreciation — a $250,000 first-year deduction
- Difference in year one: about $214,000 of additional deduction, at the owner’s marginal rate
Two honest caveats belong next to that number. First, this is acceleration, not creation: taking $250,000 now means those components generate no further depreciation later. Second, the deduction has to be usable — rental losses are generally passive, so an owner with no passive income and no qualifying exception may carry the loss forward instead of cashing it this year. The short-term rental rules and real-estate-professional status are the two common paths to using it against other income.
Is a cost segregation study worth it on a small property?
It depends on three things: the size of the short-life slice, your marginal rate, and whether you can use the loss now. A study has a real cost, and on a modest single-family rental the fee can consume much of the benefit — especially if the resulting loss is suspended as passive.
A study tends to pencil out when:
- The building basis is substantial and the property has meaningful fixtures, site work, or specialty systems
- You are in a high marginal bracket, so a deduction is worth more in cash
- You have passive income to absorb the loss, or the activity is non-passive under a qualifying exception
- You plan to hold rather than flip within a year or two, because a fast sale brings recapture forward
It tends not to pencil out on low-basis properties, in low-income years, or when a sale is imminent.
Speaking of sales: accelerated depreciation increases what gets recaptured at exit. Short-life personal property is recaptured as ordinary income, while depreciation on the real property itself is capped at a 25% rate. That trade-off is the subject of our depreciation recapture guide, and it belongs in the decision, not in a footnote after closing.
What should you do now?
- Check your dates first. Acquisition and placed-in-service dates drive whether 100% bonus applies at all.
- Get a fee quote against an estimated benefit before commissioning anything. A reputable provider will estimate the reclassification range up front.
- Confirm you can use the loss. Passive-loss rules decide whether the deduction helps this year or waits.
- Model the exit. Ask what recapture looks like on sale, and whether a 1031 exchange is part of the plan.
- Coordinate with your return. A credentialed tax professional (like an IRS Enrolled Agent) can align the study with your depreciation schedules and elections — including catch-up options on properties already in service.
FAQ
Is cost segregation legal?
Yes. It is an engineering-based allocation of purchase price among asset classes the tax code already defines. What matters is that the study is well documented and the classifications are defensible.
Can I do a cost segregation study on a property I bought years ago?
Often yes — there are established methods for catching up missed depreciation on property already in service, and they require specific forms and elections. Have a tax professional handle the mechanics.
Does the building itself qualify for bonus depreciation?
No. The structural shell never qualifies. Only the segregated short-life components and land improvements are eligible.
Does cost segregation work on residential rentals?
Yes. The structure sits on the 27.5-year residential schedule, and the same short-life components can be reclassified out of it.
Will a study create a loss I can use right away?
Not always. Rental losses are generally passive, so the deduction may be suspended and carried forward unless you have passive income or qualify for a non-passive exception.
Does accelerated depreciation increase my tax when I sell?
Yes. Faster depreciation means more to recapture at sale, with short-life property recaptured at ordinary rates and real property depreciation capped at 25%.
Sources
- IRS Publication 946: How to depreciate property
- IRS: Like-kind exchanges and real estate tax tips
- Section179.org: 2026 expensing limits
This article is for educational purposes only and is not tax, legal, or financial advice. Tax rules change and individual situations vary — consult a qualified tax professional about your specific circumstances.