Standard depreciation treats a building as a single asset with a 27.5-year life. A cost segregation study does the opposite — it breaks the property into hundreds of individual components and assigns each one a shorter life based on IRS asset classifications. The goal is to find as many components as possible that qualify for 5-year, 7-year, or 15-year depreciation schedules instead of the standard 27.5 years.
The study is performed by a team that combines engineering and tax expertise. They review construction documents, conduct a site visit, photograph components, and produce a detailed engineering report that the IRS accepts as support for the accelerated deductions. The final deliverable is a component-by-component breakdown of your property with depreciation schedules you attach to your return.
Personal property (5-year and 7-year assets) includes items that are tangible personal property rather than structural building components. In a residential rental, this includes carpet, appliances, decorative lighting fixtures, window treatments, and certain landscaping features. These items represent 10–20% of a typical residential property's value.
Land improvements (15-year assets) include parking lots, driveways, fencing, exterior lighting, landscaping, and sidewalks. These represent another 5–15% of value. The key insight is that moving these items from a 27.5-year schedule to a 5-year or 15-year schedule multiplies your early-year deduction by a factor of 5 to 18. The remaining 60–75% of the building stays on the 39-year or 27.5-year schedule, but the reclassified portion delivers outsized front-loaded benefits.
On its own, reclassifying assets into 5-year or 15-year buckets is valuable — but the annual deduction is still spread over those shorter periods. The real acceleration happens when you combine cost seg with bonus depreciation, which allows you to deduct 100% of qualifying assets in the year they are placed in service.
Under the One Big Beautiful Bill Act passed in 2025, 100% bonus depreciation has been restored for qualifying property placed in service on or after January 20, 2025. This means that all 5-year and 15-year assets identified in your cost seg study can be fully deducted in year one. On a $800,000 property where 30% gets reclassified, that is $240,000 in bonus depreciation available in the year of purchase — a deduction that would otherwise trickle out over 5 to 27.5 years.
Consider a $750,000 residential investment property in South Florida. Without cost seg, the depreciable basis (assuming 20% land) is $600,000, producing a year-one depreciation deduction of about $21,818 under straight-line.
With a cost seg study, suppose the engineer identifies $150,000 in 5-year personal property, $60,000 in 15-year land improvements, and $390,000 remaining on the 27.5-year schedule. With 100% bonus depreciation, the year-one deduction becomes $150,000 + $60,000 + $14,182 (first-year straight-line on remaining basis) = $224,182. That is more than 10 times the deduction available without cost seg. At a 37% federal marginal rate, the difference in federal tax savings between the two approaches in year one alone is approximately $74,600.
Cost segregation provides the greatest benefit to investors who can actually use the losses. High-income W-2 earners who qualify for Real Estate Professional status or who own qualifying short-term rentals can use cost seg losses to offset ordinary income — producing dollar-for-dollar tax savings at their marginal rate.
Investors who are passive (cannot meet material participation tests) still benefit, but the losses are "suspended" and carried forward until they have passive income to offset, or until they sell the property. The study is still worth doing — the deductions are not lost, just deferred. Properties with significant personal property components — furnished rentals, resort-area STRs, mixed-use buildings — tend to show the highest reclassification percentages. Properties over $500,000 in value consistently show strong ROI on the cost of the study.
Worked Example
The investor allocates 15% to land ($135,000) and $765,000 to improvements. A cost seg study identifies $191,250 (25%) in 5-year personal property and $76,500 (10%) in 15-year land improvements, with $497,250 on the standard 27.5-year schedule. With 100% bonus depreciation, the investor claims $191,250 + $76,500 = $267,750 in bonus depreciation plus $18,082 in regular depreciation in year one — a total of $285,832. The investor is in the 37% bracket and qualifies for Real Estate Professional status. The year-one federal tax savings from the accelerated deduction alone is approximately $105,758. The cost seg study cost $6,500, producing a first-year ROI of over 1,500%.
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