Accelerating depreciation on buildings
Cost segregation is an engineering study that breaks a building into its components and reclassifies the shorter-lived ones — fixtures, finishes, and land improvements — out of the long depreciation schedule that applies to the structure itself. Reclassified components depreciate far faster, pulling deductions forward into the early years of ownership, and they can interact with bonus depreciation.
Verify annually — figures adjust
The bonus depreciation percentage that applies to reclassified components was changed by the One Big Beautiful Bill Act (P.L. 119-21, signed July 4, 2025) for property acquired after early 2025. The current treatment must be confirmed against irs.gov before relying on it.
The cost is the study fee, which scales with the size and complexity of the building. Because the benefit is the time value of moving deductions forward, the fee only pays off when the property is large enough and will be held long enough for that acceleration to matter.
For tax year 2025
Key points
- Cost segregation is an engineering study, performed by an engineer, that separates a building's shorter-lived components from the structural shell so they depreciate faster.
- The study changes timing rather than the total deduction, because the building is written off once either way and acceleration is the benefit.
- Reclassified components such as fixtures, finishes, and land improvements often also qualify for bonus depreciation in the year the property is placed in service.
- Faster depreciation lowers basis, so more gain is recaptured at ordinary rates on sale, which penalises a property held only briefly.
- The IRS wants a defensible engineering methodology, with components identified, valued, and assigned to the correct recovery classes rather than estimated by rules of thumb.
What is it?
When you buy or build a commercial or rental building, the tax rules make you recover its cost slowly, over decades, through depreciation. But a building is not one thing. It contains carpeting, cabinetry, specialised electrical and plumbing, decorative lighting, and exterior land improvements such as paving and landscaping — components that the law allows to be depreciated over much shorter lives than the structure itself.
A cost segregation study is the engineering analysis that identifies and values those shorter-lived components and separates them from the building shell. Once separated, they move onto shorter depreciation schedules, so a large share of the purchase price is deducted in the early years of ownership rather than spread thinly across decades. The result is not a bigger total deduction — the building is written off once either way — but a substantial acceleration of it.
The components broken out of the shell often also qualify for bonus depreciation, which allows an additional immediate write-off in the year the property is placed in service. A study therefore does two things at once: it shifts cost into shorter recovery classes, and it makes more of the building eligible for first-year expensing. The trade-off is that faster depreciation lowers your basis, so more gain may be recaptured at ordinary rates when you sell.
Statutory basis
Who does it apply to?
Owners of commercial buildings or residential rental property with meaningful cost, who have taxable income the accelerated deductions can offset.
Buyers or builders in the year a property is placed in service, when a study can be paired with bonus depreciation for the largest early benefit.
Owners who have held a property for a few years without a study, who may be able to catch up missed depreciation through an accounting-method change.
Who does it not work for?
- A property the owner expects to sell within a short time, where the accelerated deductions are largely clawed back through depreciation recapture before they have delivered lasting benefit.
- A taxpayer with no current taxable income to absorb the deductions, since accelerated depreciation that only creates or enlarges a suspended loss delivers no immediate value.
- A building small enough that the fee for a quality engineering study outweighs the time-value benefit of moving the deductions forward.
- Owner-occupied personal residences and other property not used in a trade, business, or income-producing activity, which are not depreciable at all.
What does the IRS look at?
- Whether the study rests on a defensible engineering methodology rather than rules of thumb, with components properly identified and valued.
- Whether components were assigned to the correct recovery classes, particularly the line between structural elements and shorter-lived property.
- Whether bonus depreciation was applied only to property that genuinely qualifies.
- Whether depreciation recapture is correctly computed on sale, including the ordinary-income portion attributable to the reclassified components.
- Whether a mid-stream study uses a proper accounting-method change to claim catch-up depreciation rather than simply restating prior years.
What does it cost to fund, and when does the window close?
The cost is the study fee, which scales with the size and complexity of the building. Because the benefit is the time value of moving deductions forward, the fee only pays off when the property is large enough and will be held long enough for that acceleration to matter.
The study is performed by an engineer, often a specialist cost-segregation firm working with your CPA, who inspects the property, allocates cost among components, and documents the recovery classes. A study is most valuable in the year the property is placed in service, though a study on a property held for several years can be paired with an accounting-method change to recover missed depreciation.
Suppose you buy a small commercial building for $2,000,000, of which $400,000 is land. A study might reclassify roughly 25% of the $1,600,000 building basis — about $400,000 — into components with 5-, 7-, and 15-year lives, much of which can be expensed in year one rather than spread over decades.
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Related strategies
- §168Immediate expensing of equipmentCapital outlay
- §481Catching up missed depreciation without amendingNo outlay
- §469Buying the building your business operates fromCapital outlay
Common questions
- Does cost segregation increase my total deductions?
- No. The building is depreciated once either way, so a study does not enlarge the total write-off. What it changes is timing: it moves a large share of the cost into shorter recovery classes, so the deductions land in the early years of ownership instead of being spread thinly across decades. The benefit is the time value of holding those deductions sooner, claimed through the depreciation schedule on Form 4562.
- What happens to the accelerated depreciation when I sell?
- Depreciation reduces your basis, so a faster write-off leaves more gain on sale, and the part attributable to the reclassified personal property is recaptured as ordinary income rather than capital gain. That recapture is computed on Form 4797 for the year of sale. It is why a property you expect to sell within a few years is a poor candidate: the recapture can undo much of the early benefit.
- Can I do a study on a building I have owned for years?
- Often yes. A study on a property held for several years can be paired with an accounting-method change filed on Form 3115, which claims the depreciation you could have taken as a single catch-up adjustment in the current year instead of amending prior returns. A CPA prepares that filing, and the engineering firm supplies the component analysis it rests on.
Mena Hemaia, CPA, CIA
Chief Executive Officer, Accountack — West Palm Beach, Florida
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