You bought a building for $3,200,000. Your CPA put one number on the depreciation schedule and divided it by 27.5. That is not wrong, but it is incomplete. The carpet, the cabinets, and the parking lot were never 27.5-year assets. Cost segregation is the engineering work that proves it.
The short answer
- Cost segregation reclassifies portions of a building from 27.5- or 39-year real property into 5-, 7-, and 15-year property, so those costs are deducted years or decades sooner.
- A typical study moves 20% to 30% of depreciable basis into shorter lives. Restaurants, hotels, medical offices, and self-storage often reach 30% to 45%. Plain warehouses run 10% to 18%.
- It is not an election or a loophole. It applies MACRS rules, supported by Hospital Corporation of America v. Commissioner, 109 T.C. 21 (1997).
- 100% bonus depreciation is permanent again, so most reclassified property can be written off entirely in year one.
- This defers tax, it does not erase it. The benefit is time value of money, and there is real recapture exposure when you sell.
What Cost Segregation Actually Is
You recover the cost of income property through depreciation: 27.5 years for residential rental, 39 years for nonresidential. Most closings produce one lump number, and everything inside it inherits the long life.
A study takes that lump apart. An engineer inspects the property, quantifies each component, and assigns it to the recovery period the code prescribes. Cabinetry, decorative lighting, carpet, appliances, window treatments, and circuits dedicated to specific equipment are generally 5-year property. Paving, sidewalks, site utilities, fencing, landscaping, and signage are 15-year land improvements. The structure stays at 27.5 or 39.
The dividing line is permanence and function, the test applied in Whiteco Industries v. Commissioner, 65 T.C. 664 (1975). A load-bearing wall is structure; a demountable partition is not. Nothing here is invented: those costs already sit in your purchase price, and land comes out first.
How Much Gets Reclassified: A Worked Example
Example: a $3,200,000 apartment building placed in service in January Land allocated at $500,000, leaving $2,700,000 of depreciable basis. The engineer finds $410,000 of 5-year personal property and $240,000 of 15-year land improvements, or 24% of basis. The 27.5-year structure uses the MACRS mid-month convention, which for a January placement gives a first-year factor of 3.485%, not a full 1/27.5.
| Without a study | With a study | |
|---|---|---|
| 5-year property | $0 | $410,000 |
| 15-year land improvements | $0 | $240,000 |
| 27.5-year structure | $2,700,000 | $2,050,000 |
| Year-one deduction | $94,095 | $721,443 |
| Cash value of the difference at 35% | ~$219,600 |
Your result depends on your tax rate and whether you can use passive losses.
Why Permanent 100% Bonus Depreciation Changed the Math
Bonus depreciation turns a reclassification into cash. Property with a recovery period of 20 years or less is eligible, which covers everything a study pulls out of the long-life bucket.
The One Big Beautiful Bill Act, signed July 4, 2025, restored 100% bonus depreciation permanently under §168(k) for property acquired and placed in service after January 19, 2025. Used property qualifies if bought from an unrelated party.
Two details surprise owners. Property acquired on or before that date still follows the old phase-down, so a 2024 acquisition gets 60%. And the rate is locked to the original placed-in-service date, not the study date, so a 2021 building studied today still gets 2021's 100%. See the 2026 bonus depreciation rules.
Who Can Actually Use the Deduction
A deduction you cannot deploy this year is worth less than one you can. Under §469, rental losses are passive by default and offset only passive income.
The routes around that are Real Estate Professional Status (more than 750 hours in real property trades or businesses, more than half of all personal services, and then material participation in the rental activity itself, or a §469(c)(7)(A) election to treat all rentals as one activity), the short-term rental exception for properties averaging seven days or less per stay where you materially participate, or other passive income to absorb the loss. There is also a ceiling: §461(l) caps 2026 net business losses at $256,000 single / $512,000 married filing jointly. Check the passive activity loss rules first.
What You Actually Receive
An engineering report, not a spreadsheet. A defensible study documents its methodology, shows the quantities and unit costs behind every allocation, includes photographs and the legal analysis for each classification, lists §1245 property asset by asset, and reconciles allocated costs to total actual cost. Those are among the 13 elements the IRS Audit Techniques Guide associates with a quality study.
Your CPA takes the asset schedule and files. On a building owned for years, the catch-up runs through Form 3115 with a §481(a) adjustment taken entirely in the year of change, and no amended returns. See the step-by-step study process.
The Honest Part: Deferral, Not Elimination
Faster depreciation reduces basis faster, which means more gain on sale. Reclassified 5-, 7-, and 15-year assets are §1245 property, and gain up to the depreciation taken returns as ordinary income at rates up to 37%. The structure is §1250 property, taxed at a maximum 25% on unrecaptured gain.
So the real question is arbitrage. You deduct today at your marginal rate, pay later at recapture rates, and use the money in between. That is a good trade on a long hold, with a §1031 exchange planned, or where the §1014 step-up at death erases the exposure for heirs. It is a poor trade if you sell in two years or the loss sits suspended. See whether cost segregation is worth it and depreciation recapture.
Frequently Asked Questions
Is cost segregation legal?
Yes. It applies existing MACRS rules to assets you already own. The Tax Court validated component-based segregation in Hospital Corporation of America in 1997, and the IRS publishes an Audit Techniques Guide, revised February 2025, describing what a quality study looks like. The risk is not the strategy; it is a weak study.
Can I do this on a building I bought years ago?
Yes. There is no cutoff on the catch-up. A look-back study computes the depreciation you should have taken, and Form 3115 brings it onto the current return as a §481(a) adjustment taken 100% in the year of change, with no amended returns.
Does a study increase my audit risk?
Accelerated depreciation is an area examiners understand well. What protects you is documentation: methodology, unit costs, photographs, and reconciliation to actual cost. Studies that draw scrutiny are built from rules of thumb, not measured components. The audit-flag fear is one of several claims that do not survive contact with the record, which we take apart in the most common cost segregation myths.
See What Your Property Would Yield
Every building is different, and the only way to know your number is to look at your building. Precision Cost Segregation provides a no-cost feasibility analysis: send us the property address, purchase price, closing date, and any improvements, and we'll model your likely reclassification and first-year benefit before you commit to anything.
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This article is provided by Precision Cost Segregation for general educational purposes and does not constitute tax, legal, or accounting advice. Tax outcomes depend on your specific facts, your tax rate, your passive activity position, and your entity structure. Figures shown are illustrative. Consult your CPA or tax advisor before acting, and engage a qualified professional to perform any cost segregation study. Information is current as of publication.
This article is general information, not tax or legal advice. Depreciation outcomes depend on your facts, elections, and current law — consult your CPA before acting. © 2026 Precision Cost Segregation.