HOW-TO GUIDE
How to Do a Cost Segregation Study — Practitioner Guide 2026
Step-by-step guide to cost segregation studies — qualifying properties, study methodology, bonus depreciation interaction, and how to identify cost segregation candidates with Kam Code.
Cost Segregation: The Most Powerful Real Estate Tax Strategy
Cost segregation is the process of reclassifying components of a real property from 39-year (commercial) or 27.5-year (residential) depreciation to 5-year, 7-year, or 15-year depreciation. The result: dramatically accelerated depreciation deductions in the early years of ownership, producing large tax savings.
A cost segregation study on a $1,000,000 commercial property typically identifies 20–40% of the cost as personal property (5-year or 7-year) and land improvements (15-year). With 100% bonus depreciation (restored by OBBBA for property placed in service after Jan 19, 2025) in 2025, the first-year deduction can be $150,000–$250,000 — compared to $25,641 under straight-line 39-year depreciation. The tax savings at a 37% marginal rate: $55,500–$92,500 in year one alone.
| Property Type | Study Cost | Typical Reclassification | First-Year Deduction (2025) | Tax Savings (37%) |
|---|---|---|---|---|
| Residential rental ($500K) | $3,500–$6,000 | 15–25% to 5/7/15-yr | $30,000–$60,000 | $11,100–$22,200 |
| Commercial ($1M) | $5,000–$10,000 | 20–35% to 5/7/15-yr | $80,000–$140,000 | $29,600–$51,800 |
| Commercial ($3M) | $8,000–$15,000 | 20–35% to 5/7/15-yr | $240,000–$420,000 | $88,800–$155,400 |
| Hotel/Hospitality ($5M) | $12,000–$20,000 | 25–40% to 5/7/15-yr | $500,000–$800,000 | $185,000–$296,000 |
Step-by-Step Cost Segregation Process
Step 1 — Identify Qualifying Properties: Cost segregation is most valuable for: (1) commercial properties over $1,000,000; (2) residential rental properties over $500,000; (3) properties purchased or constructed in the last 15 years (look-back studies available); and (4) properties with significant improvements. The study is not cost-effective for properties under $300,000 or properties that will be sold within 1–2 years (depreciation recapture will offset the benefit).
Step 2 — Hire a Qualified Cost Segregation Firm: Cost segregation studies must be performed by a qualified engineer or cost segregation specialist. The study involves a site visit, review of construction documents, and a detailed analysis of each building component. Cost: $3,500–$20,000 depending on property size and complexity. The study report must meet IRS requirements (Rev. Proc. 2011-43).
Step 3 — Review the Study Report: The study report will identify each building component, its cost, and its assigned asset class (5-year, 7-year, 15-year, or 39-year). Review the report for accuracy and completeness. The report should include a detailed description of each component and the basis for the asset class assignment.
Step 4 — Apply bonus depreciation is 100% permanent (OBBBA restored it) from 60% in 2024 to 20% in 2026). Apply bonus depreciation to the reclassified components in the year the study is completed.
Step 5 — Consider the Passive Activity Rules: Real estate depreciation deductions are generally passive activity losses, which can only offset passive income. The exception: real estate professionals (IRC §469(c)(7)) who spend more than 750 hours per year in real estate activities can treat real estate losses as non-passive. For non-real estate professionals, the passive activity losses carry forward until the property is sold.
Look-Back Studies: Catching Up on Missed Depreciation
If a client purchased a qualifying property in a prior year without a cost segregation study, they can still benefit through a look-back study. A look-back study reclassifies the property retroactively and allows the client to catch up on all missed depreciation in the current year — without amending prior returns. The catch-up depreciation is reported on Form 3115 (Application for Change in Accounting Method) as a Section 481(a) adjustment.
Look-back studies are available for properties purchased within the last 15 years. The catch-up depreciation can be substantial — a $2,000,000 commercial property purchased 5 years ago might have $300,000–$500,000 in missed depreciation that can be deducted in the current year.
Case Study: $148,000 First-Year Deduction on a $1.2M Property
Robert, a real estate investor, purchased a $1,200,000 commercial building in 2025. His practitioner identified the cost segregation opportunity using Kam Code and hired a qualified cost segregation firm ($8,500 study cost). The study identified: $180,000 in 5-year personal property; $120,000 in 15-year land improvements; $900,000 in 39-year building. With 100% bonus depreciation (restored by OBBBA for property placed in service after Jan 19, 2025): 5-year deduction = $72,000; 15-year deduction = $48,000; 39-year deduction = $23,077. Total first-year deduction: $143,077 (vs. $30,769 without cost segregation). Tax savings at 37%: $52,938 (vs. $11,384 without). Net benefit after study cost: $44,438 in year one.
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Join Uncle Kam →Frequently Asked Questions
Cost segregation is the process of reclassifying components of a real property from 39-year (commercial) or 27.5-year (residential) depreciation to 5-year, 7-year, or 15-year depreciation. The result is dramatically accelerated depreciation deductions in the early years of ownership.
Cost segregation is most valuable for commercial properties over $1,000,000 and residential rental properties over $500,000. Properties purchased or constructed in the last 15 years are eligible for look-back studies. The study is not cost-effective for properties under $300,000.
A look-back study reclassifies a property purchased in a prior year and allows the client to catch up on all missed depreciation in the current year — without amending prior returns. The catch-up depreciation is reported on Form 3115 as a Section 481(a) adjustment.
Real estate depreciation deductions are generally passive activity losses, which can only offset passive income. The exception: real estate professionals (IRC §469(c)(7)) who spend more than 750 hours per year in real estate activities can treat real estate losses as non-passive. For non-real estate professionals, passive activity losses carry forward until the property is sold.
When a property is sold, previously deducted depreciation is recaptured as ordinary income (Section 1250 recapture) or taxed at a maximum 25% rate (unrecaptured Section 1250 gain). Cost segregation accelerates depreciation but also accelerates recapture — consider the recapture impact before recommending a study for a property that will be sold soon.
Look for firms that are members of the American Society of Cost Segregation Professionals (ASCSP) or have engineers on staff with experience in IRS Rev. Proc. 2011-43 compliant studies. Get quotes from 2–3 firms and review sample reports before hiring. The study cost should be 1–3% of the property value for most properties.