Cost Segregation vs. Standard Depreciation
How depreciation differs when a property is treated as one building versus separated into components, and what changes — and what does not — when you use a study. Total depreciable basis stays the same. Timing, method, and recapture character can change.
Educational information, not tax advice.
Updated 2026-10-14
Key takeaways
- Standard practice treats nearly all of a property's cost (minus land) as a single 27.5- or 39-year building.
- Cost segregation splits out components that qualify for 5-, 7-, or 15-year recovery.
- Total depreciation over the life of the property is the same; the timing differs.
- Shorter classes often use declining-balance methods and can qualify for bonus depreciation.
- Land never becomes depreciable, and a study does not raise basis above cost.
Without a study, a typical approach is to allocate the purchase price between land and building, and depreciate the building straight-line over 27.5 or 39 years using the mid-month convention. That is a permitted method, but it may put shorter-lived components in the wrong class.
With a study, the depreciable cost is broken into classes. Personal property such as appliances and dedicated equipment wiring might be 5-year property, recovered using the 200% declining-balance method. Land improvements such as parking lots and fencing are generally 15-year property, recovered using 150% declining balance. What remains is the building.
Both approaches start from the same cost. Section 1012 generally sets basis at cost. Land is removed because it cannot be depreciated. The study reallocates the depreciable remainder. It does not create basis that was not in the purchase or construction cost.
The first-year difference can be large when shorter-lived property also qualifies for bonus depreciation. As of October 16, 2026, that additional first-year allowance is 100% for qualified property acquired after January 19, 2025. Earlier binding-contract property stays on the phase-down schedule.
The comparison is incomplete if it stops at year one. Later-year building deductions are smaller after a study, adjusted basis falls faster, and §1245 recapture can be larger on sale. Educational information, not tax advice.
What changes
Deductions in early years go up because shorter classes use faster methods and shorter periods, and because many of those components can qualify for bonus depreciation. Later-year deductions go down by the same total amount.
Conventions change with the class. Buildings use the mid-month convention. Personal property generally uses the half-year convention, or the mid-quarter convention if more than 40% of the year’s personal-property basis is placed in service in the last three months. Real property is excluded from that 40% test.
Form 4562 reporting also changes. Bonus, if claimed, is taken after any §179 election and before regular MACRS. Your CPA decides those elections. A study supplies the class and cost support; it does not elect anything.
What does not change
The total cost being depreciated stays the same, and so does the land, which is never depreciable. A study also does not change the rules for selling: depreciation on §1245 property is generally recaptured as ordinary income, while recapture on buildings under §1250 is limited to depreciation in excess of straight-line.
The statutory lives of the building itself stay 27.5 or 39 years. Cost segregation does not shorten a wall, a roof, or central building HVAC by calling the structure something else. Those items remain structural components unless the facts and the regulations say otherwise. The comparison is about class mix, not about inventing a shorter life for the building.
State returns may not follow the federal timing. California, for example, does not conform to §168(k). A federal first-year difference can shrink or disappear on a state return. That is a CPA question, not a study conclusion.
When the simpler approach may be enough
For a low-cost property, a property you expect to sell soon, or a situation where you cannot use the extra deductions, the benefit of a study may be small. Your CPA can compare both approaches for your facts.
Passive activity limits, taxable-income limits on §179, and a short remaining holding period can defer or reduce the cash-flow effect. A study that is correct on classification can still be a poor fit for the return.
Properties with almost no removable personal property or site work — a bare warehouse shell on unimproved land, for example — often have less to reclassify. The analysis still starts with the records, not with an assumed percentage. A small first-year difference can still be the correct answer when the facts support few shorter-lived components.
How to read a side-by-side comparison
A useful comparison holds basis, placed-in-service date, and bonus eligibility constant and changes only the class mix. It should show early-year deductions, later-year deductions, and remaining basis — not only the first year.
Hypothetical percentages from marketing materials are not a substitute for that comparison. Cost segregation does not have a standard “reclassification rate,” and no figure in this library is a typical result.
Implementing the change
If the property is placed in service in the current year and has not yet appeared on a return, the study’s classes are used on the first Form 4562. That is a classification decision, not a method change.
If prior returns already depreciated the improvement as one building, switching classes is generally a change in accounting method. The usual path is Form 3115 and a §481(a) adjustment. See the look-back and Form 3115 articles in this group.
Sources
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- 4IRS Publication 946 — How To Depreciate Property (2025)(opens in a new tab)
Appendix B reproduces the Rev. Proc. 87-56 class lives.
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