A cost segregation study reclassifies parts of a building from 27.5- or 39-year property into 5-, 7- and 15-year property so their depreciation arrives sooner, and bonus depreciation can expense them in year one: 100% for qualified property acquired after January 19, 2025, or 20% for property acquired on or before that date and placed in service in 2026.
This guide is the reference for deciding whether, when and how to order a study; for the plain-English definition alone, read what a cost segregation study is, in plain English.
What Does a Cost Segregation Study Reclassify?
A cost segregation study is a tax analysis that reclassifies components of a real property from long-lived structural assets — which depreciate over 27.5 or 39 years — into shorter-lived personal property and land improvements that depreciate over 5, 7, or 15 years.
The result: depreciation deductions accelerate into the early years of ownership, generating tax savings precisely when your cash flow matters most.
The IRS formally recognized cost segregation as a legitimate tax planning strategy in the landmark 1997 decision Hospital Corporation of America v. Commissioner, 109 T.C. 21 (1997), which upheld the reclassification of building components into personal property categories. The IRS subsequently codified its approach in the Cost Segregation Audit Techniques Guide (ATG), first published in 2004 and regularly updated.
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The Four Recovery Periods That Matter
Under the Modified Accelerated Cost Recovery System (MACRS) established by IRC §168 and Treasury Regulation §1.168, real property components fall into four primary recovery categories:
- 5-year property: Tenant-serving fixtures and systems — specialty flooring, dedicated electrical systems for equipment, security systems, decorative lighting, certain HVAC components. Depreciated at 200% declining balance.
- 7-year property: General office furniture and equipment, certain specialty assets. Depreciated at 200% declining balance.
- 15-year property: Land improvements — parking lots, sidewalks, fencing, landscaping, outdoor lighting, site utilities. Depreciated at 150% declining balance.
- 27.5-year or 39-year property: The structural shell, foundation, roof, and building systems that serve the building as a whole. Residential rental property uses 27.5 years; non-residential commercial real property uses 39 years.
Who Should Get a Study?
A common industry rule of thumb is that cost segregation makes economic sense when the depreciable basis exceeds $500,000 — but that number is a pricing threshold for a study priced in the thousands of dollars, not a tax rule. Run the same arithmetic against a $499* cost segregation workpaper and the floor is lower. Whenever you see a basis threshold quoted, ask what study fee it assumes — what a cost segregation study costs in 2026 lists our prices and other providers' published prices. Above $1 million in depreciable basis, the return on investment becomes compelling across virtually all property types, and a $14M study taken line by line shows how that return is actually built.
*For a property whose purchase price plus construction costs total under $2.0 million.
The strongest candidates are properties recently purchased, newly constructed, or significantly renovated within the last 15 years. A look-back study can reach a property you placed in service in an earlier tax year and still own: Under the automatic change procedures of Rev. Proc. 2015-13 and section 6.01 of Rev. Proc. 2025-23, the missed depreciation is claimed on Form 3115 with no amended returns when the property has been depreciated on two or more filed returns, or on one filed return if the taxpayer placed it in service in the tax year immediately before the year of change (the year of the return the Form 3115 is filed with), and the taxpayer still owned the property at the start of the year of change and meets the other eligibility rules. The catch-up is then taken in a single year as a §481(a) adjustment.
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How Are Short-Life Components Identified?
The analysis at the heart of a cost segregation study involves reviewing construction documents — AIA pay applications, contractor schedules, and general contractor breakdowns — and documenting the property itself, by a site inspection or, on this platform, by photographs. Each line item is classified to the appropriate MACRS recovery period based on its function, permanence, and relationship to the building structure.
The IRS ATG describes the detailed engineering approach from actual cost records (Ch. 3, C.1) as, in general, "the most methodical and accurate approach," because it uses actual construction costs as the basis for component allocation; the IRS has not established a required method (Ch. 3, D). This approach carries the strongest documentary support and produces the most accurate results.
How Much Does Cost Segregation Reclassify by Property Type?
The percentage of depreciable basis that can be reclassified to shorter lives varies significantly by property type. These are planning bands, not promises, each a share of the depreciable basis (purchase price plus construction costs, less land), and the IRS Cost Segregation Audit Techniques Guide itself publishes no reclassification percentages:
- Restaurant/QSR: no published planning band; the share that moves to 5- and 15-year property depends on the property's own cost detail — see restaurant cost segregation and why QSR and restaurant properties are the strongest cost segregation candidates.
- Self-Storage: typically 40–55% of the depreciable basis (a planning band, not a promise) — see how self-storage cost segregation works, with a worked example and why self-storage is the category most investors overlook.
- Commercial Office: typically 20–30% reclassified
- Multifamily: typically 20–30% of the depreciable basis (a planning band, not a promise) — see what a multifamily cost segregation study typically reclassifies and the build-to-rent blind spot for SFR rental communities.
- Retail: typically 25–35% reclassified — see retail cost segregation.
- Industrial/Warehouse: typically 15–22% reclassified
Short-term rentals sit slightly apart from the categories above; cost segregation on a short-term rental covers that case on its own terms.
Why Is Cost Segregation Most Powerful With Bonus Depreciation?
Cost segregation is most powerful when combined with IRC §168(k) bonus depreciation, which allows immediate expensing of qualified property in the year it is placed in service. Under the Tax Cuts and Jobs Act of 2017 (TCJA), bonus depreciation was set at 100% for property acquired and placed in service after Sept. 27, 2017. Bonus depreciation under IRC §168(k) is 100%, permanently, for qualified property acquired after January 19, 2025 (OBBBA, 2025-07-04), or, for self-constructed property, whose construction began after that date; qualified property acquired on or before that date stays on the TCJA phase-down (as does self-constructed property begun on or before it) by placed-in-service year: 80% in 2023, 60% in 2024, 40% in 2025, 20% in 2026, and 0% after that, with each rate one year later for long-production-period property and certain aircraft (§168(k)(6)(B)). For the full analysis of both rules, see which bonus depreciation rate applies in 2026, by acquired date.
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The Bottom Line
A well-executed cost segregation study is not a tax gimmick — it is a proper application of federal tax law that every commercial property owner should consider. The IRS ATG explicitly validates the methodology, and the case law supporting it is robust. The only question is whether your property and tax situation make it economical, which depends on the basis against the fee, whether the deduction is usable this year, and the hold period.
Put your own building through the math on our free cost segregation calculator — it takes minutes and shows the estimated first-year deduction before you spend anything. To weigh providers first, how cost segregation firms compare lays out the market, and a cost segregation study applies the recovery periods above to a specific property.
Frequently Asked Questions
What recovery periods does a cost segregation study use?
A cost segregation study sorts a building's cost under the MACRS rules of IRC §168 into 5-year property (tenant-serving fixtures and systems), 7-year property (certain furniture and specialty assets), 15-year land improvements (paving, landscaping, site utilities) and the structure itself, which is 27.5-year property for residential rental buildings and 39-year property for nonresidential buildings.
Is a cost segregation study worth it for my property?
A cost segregation study is worth it when three conditions hold together: the basis is large enough for the accelerated deductions to outweigh the cost of the study, the deduction is usable this year given the owner's passive-activity position, and the hold is long enough to survive recapture. All three, or the honest answer is no. Is cost segregation worth it? walks the math line by line.
Can a cost segregation study cover a property bought in an earlier year?
Yes, a cost segregation study can cover a property you placed in service in an earlier tax year and still own, as a look-back study. Under the automatic change procedures of Rev. Proc. 2015-13 and section 6.01 of Rev. Proc. 2025-23, the missed depreciation is claimed on Form 3115 with no amended returns when the property has been depreciated on two or more filed returns, or on one filed return if the taxpayer placed it in service in the tax year immediately before the year of change (the year of the return the Form 3115 is filed with), and the taxpayer still owned the property at the start of the year of change and meets the other eligibility rules. Form 3115 catch-up depreciation covers the filing.
How does bonus depreciation work with a cost segregation study in 2026?
Bonus depreciation applies only to property with a recovery period of 20 years or less, so a cost segregation study is what identifies the 5-, 7- and 15-year property inside a building that bonus depreciation can expense in the year it is placed in service. Bonus depreciation under IRC §168(k) is 100%, permanently, for qualified property acquired after January 19, 2025 (OBBBA, 2025-07-04), or, for self-constructed property, whose construction began after that date; qualified property acquired on or before that date stays on the TCJA phase-down (as does self-constructed property begun on or before it) by placed-in-service year: 80% in 2023, 60% in 2024, 40% in 2025, 20% in 2026, and 0% after that, with each rate one year later for long-production-period property and certain aircraft (§168(k)(6)(B)). The acquired-date test settles which rate applies.
Which cost segregation method does the IRS call the most accurate?
The IRS Cost Segregation ATG describes the detailed engineering approach from actual cost records (Chapter 3, C.1) as, in general, the most methodical and accurate approach because it uses actual construction costs, and it also says the IRS has not established a required method (Chapter 3, D).
