Cost Segregation: Convert Decades of Depreciation Into First‑Year Deductions

A Cost Segregation study is an engineering-based analysis that reclassifies building components from the standard 27.5 or 39-year depreciation schedule into shorter recovery categories of 5, 7, and 15 years. With 100% bonus depreciation permanently restored under the One Big Beautiful Bill Act for qualifying property acquired and placed in service after January 19, 2025, reclassified assets are fully deductible in the year the property is placed in service. A typical study identifies 20 to 40% of a building's depreciable basis as eligible for accelerated recovery. The IRS Cost Segregation Audit Techniques Guide establishes the standards examiners use to evaluate study quality; engineering-based analysis following ATG methodology produces documentation built for audit defense.

179D should be evaluated first. Under IRC §179D(e), the 179D deduction reduces the basis of the property that earns it by the amount of the deduction. Cost Segregation then reclassifies remaining components from the adjusted basis into shorter recovery categories. Running a Cost Segregation study without evaluating 179D can leave the 179D deduction unclaimed or overstate the basis the study depreciates. Evaluating both together applies that basis reduction correctly and shows the combined first-year benefit.

Any taxpayer who owns depreciable real property qualifies: commercial buildings (39-year), residential rental properties (27.5-year), and mixed-use properties. The property can be newly constructed, purchased, or renovated. Properties placed in service in prior years are eligible through a look-back study. Most professionals recommend a minimum of $200,000 for residential or $750,000 for commercial to ensure the study cost is justified by the tax benefit. Some companies also qualify for R&D tax credits alongside building incentives, particularly in manufacturing, engineering, and technology sectors.

Gain on 5 and 7-year assets is subject to Section 1245 recapture at ordinary income rates, up to the depreciation taken. On 15-year land improvements and qualified improvement property, depreciation above the straight-line amount, including bonus, is generally recaptured as ordinary income under Section 1250, and for individuals the remaining gain from depreciation on the building and other real property is taxed at a maximum rate of 25%. The time value of accelerated deductions can outweigh the recapture at sale, particularly over longer holding periods. Since 2018, 1031 like-kind exchanges cover only real property, so recapture on 5 and 7-year components can be triggered even when the rest of the gain is deferred.

Yes. A look-back study captures all missed accelerated depreciation from prior years. The adjustment is claimed in the current tax year through IRS Form 3115 as an automatic change in accounting method under Section 481(a). No amended returns required. The entire catch-up deduction flows through the current year return. There is no set age limit; the benefit depends on how much depreciation the building has left.

Bonus depreciation under IRC §168(k) allows qualifying assets with recovery periods of 20 years or less to be deducted in the year placed in service. The One Big Beautiful Bill Act permanently restored 100% bonus depreciation for property acquired and placed in service after January 19, 2025, so every 5, 7, and 15-year asset a Cost Segregation study identifies on those properties can be deducted in year one. Property acquired before January 20, 2025 keeps the earlier phase-down: 80% if placed in service in 2023, 60% in 2024, 40% in 2025, 20% in 2026, and none after 2026. For property the owner constructs, the acquisition date is generally when significant physical work began, so a building whose construction started before January 20, 2025 may have some components on the phase-down. Our Cost Segregation Guide has the full table.

Qualified Improvement Property (QIP) covers improvements a taxpayer makes to the interior of a nonresidential building after the building was first placed in service, other than enlargements, elevators and escalators, and the internal structural framework. QIP is 15-year property eligible for bonus depreciation, 100% when acquired after January 19, 2025. A Cost Segregation study can identify components within a renovation that qualify for even shorter recovery periods of 5 or 7 years, providing more accelerated treatment than QIP's 15-year classification. For renovation projects that also involve HVAC, lighting, or envelope improvements, 179D should be evaluated alongside both QIP and Cost Segregation to determine the optimal classification strategy. Your tax advisor can help determine the approach that produces the best total outcome for your specific project.

Most studies are completed within 30 to 60 days depending on property complexity and documentation availability. The timeline begins once construction documents and cost records are received. Studies involving look-back adjustments on existing properties typically fall within the same timeframe.