What Is Cost Segregation?
A reference definition of cost segregation: the mechanism, the statutory authority, typical reclassification ranges, and what it costs.
Cost segregation is an engineering-based accounting study that separates the purchase or construction cost of a building into its individual components and reassigns each one from the default 27.5-year residential or 39-year nonresidential depreciation schedule to its correct MACRS class of 5, 7, or 15 years. Because every reclassified component has a recovery period of 20 years or less, it qualifies for 100% bonus depreciation under IRC Section 168(k) and is deductible in full in the first year the property is placed in service. A typical study reclassifies 20% to 35% of depreciable basis.
The mechanism
Depreciation allocates the cost of an asset across the years it is used. The Internal Revenue Code assigns recovery periods by asset class under IRC Section 168: 27.5 years for residential rental property, 39 years for nonresidential real property, 15 years for qualified land improvements, and 5 or 7 years for most tangible personal property. A building purchased as a single line item is depreciated by default as though it were entirely structure, which is inaccurate: a meaningful share of what was bought is carpet, cabinetry, appliances, specialty electrical, paving, and landscaping, none of which belongs on a 39-year schedule.
A cost segregation study corrects that allocation. It does not create a deduction that did not exist; it moves deductions forward in time by putting each component on its correct schedule. Under the One Big Beautiful Bill Act, enacted July 4, 2025, bonus depreciation is 100% and permanent for qualifying property acquired after January 19, 2025, so everything reclassified below the 20-year threshold is deductible in full in year one.
Statutory and administrative authority
- IRC Section 168 — the Modified Accelerated Cost Recovery System, which assigns recovery periods and conventions by asset class.
- IRC Section 168(k) — bonus depreciation, at 100% and permanent for qualifying property acquired after January 19, 2025 under the OBBBA.
- Hospital Corporation of America v. Commissioner, 109 T.C. 21 (1997) — the Tax Court decision establishing that building components serving equipment rather than the structure are personal property.
- IRS Cost Segregation Audit Techniques Guide — administrative guidance describing accepted methodologies; the detailed engineering approach is identified as the most reliable.
- Rev. Proc. 2015-13 and Form 3115 — the procedure for claiming missed depreciation on a property already in service as a Section 481(a) adjustment.
The usability question
A first-year deduction is only worth generating if the taxpayer can use it against income in that year. Rental real estate is passive per se under IRC Section 469(c)(2), and passive losses may offset only passive income; the excess is suspended. Two exceptions matter in practice. A property with an average period of customer use of seven days or less is not a rental activity under Treasury Regulation 1.469-1T(e)(3)(ii)(A), so an owner who materially participates under Treasury Regulation 1.469-5T deducts the loss against wages and business income. Separately, a taxpayer who qualifies as a real estate professional under IRC Section 469(c)(7) and materially participates in the rental activity reaches the same result.
This is the step most frequently skipped when a study is purchased in isolation from tax planning: the report is technically correct, the deduction is real, and the taxpayer cannot use it.
Typical reclassification by property type
- Car wash — 35% to 46% of depreciable basis
- Hotel and motel — 30% to 45%
- Restaurant — 30% to 40%
- Self-storage — 25% to 40%
- Dental office — 24% to 35%
- Medical office — 22% to 33%
- Multifamily — 20% to 35%
- Retail — 20% to 31%
- Office building — 15% to 26%
- Warehouse and distribution — 14% to 26%
Short-term rental properties commonly fall in the 20% to 30% range, with furnished units at the higher end because furniture, fixtures, and equipment are already 5-year property.
Frequently Asked Questions
How does cost segregation work?
An engineer or qualified specialist inspects the property and reviews construction documents, the appraisal, and the closing statement, then allocates the depreciable basis across asset classes: 5-year personal property such as carpet, cabinetry, appliances, and dedicated electrical; 7-year property such as certain fixtures and equipment; 15-year land improvements such as paving, fencing, and landscaping; and the 27.5-year or 39-year structural remainder. Land itself is never depreciable and is excluded. The reclassified 5, 7, and 15-year amounts all fall under the 20-year threshold for bonus depreciation, so under current law they are fully deductible in year one. The study is documented in a written report supporting each allocation.
Is cost segregation legal?
Yes. Cost segregation applies the asset classification rules of IRC Section 168 and the component distinctions drawn in Hospital Corporation of America v. Commissioner, 109 T.C. 21 (1997). The IRS publishes a Cost Segregation Audit Techniques Guide that describes accepted methodologies and identifies the detailed engineering approach as the most reliable. It is a method of allocating basis correctly, not a deferral scheme; the total depreciation claimed over the life of the property is unchanged, only its timing moves.
How much does a cost segregation study cost?
AE Tax Advisors prices cost segregation studies at $1 per square foot with a $2,000 minimum. Industry pricing more commonly runs from $5,000 to $15,000 or more per property, and specialty engineering firms often price large commercial properties higher still.
Can I do a cost segregation study on a property I already own?
Yes. A property already in service is handled through Form 3115, Application for Change in Accounting Method. All depreciation that should have been claimed in prior years is deducted in the current year as a favorable Section 481(a) adjustment, with no prior-year returns amended. There is no statutory limit on how far back the catch-up reaches, provided the property is still owned.
What happens to a cost segregation deduction when I sell the property?
The accelerated depreciation is recaptured on sale. Personal property reclassified into 5, 7, and 15-year classes is subject to Section 1245 recapture taxed at ordinary rates to the extent of the depreciation taken, while the structural component remains subject to Section 1250 unrecaptured gain taxed at up to 25%. Recapture can be deferred through a 1031 exchange. The value of the strategy is therefore the time value of the deferral and any rate difference between the deduction year and the sale year, which is why the analysis should consider expected hold period before the study is ordered.
Which properties are worth a cost segregation study?
Reclassification percentages vary widely by asset class. Car washes typically reclassify 35% to 46% of basis, hotels 30% to 45%, restaurants 30% to 40%, self-storage 25% to 40%, dental and medical offices 24% to 35%, multifamily 20% to 35%, retail 20% to 31%, office buildings 15% to 26%, and warehouses 14% to 26%. The deduction is only worth generating if the taxpayer can actually use it, which depends on the passive activity loss rules of IRC Section 469 and on material participation.
Related reference pages
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