How does a cost segregation study work?

What it is

When you buy, build, or improve a building, most of the cost is depreciated over a long recovery period. A cost segregation study, usually prepared by engineers or specialists, allocates part of the cost to shorter-lived property such as certain electrical and plumbing serving equipment, specialty finishes, cabinetry, carpeting, and land improvements like paving, fencing, and landscaping.

The total depreciation over the life of the property does not change. The study moves deductions earlier, which can improve cash flow when the deductions reduce tax you would otherwise pay.

What the law says

IRC §168(c) assigns a 27.5-year recovery period to residential rental property and 39 years to nonresidential real property. IRC §168(k), as amended by P.L. 119-21, allows a 100% additional first-year depreciation deduction for qualified property acquired after January 19, 2025. Qualified property generally has a recovery period of 20 years or less. IRS Notice 2026-11 provides interim guidance on the acquisition-date rules and elections.

IRC §1245 recaptures depreciation on personal property as ordinary income when the property is sold. The IRS Cost Segregation Audit Techniques Guide describes the features examiners look for in a quality study.

Requirements and tests

A study supports faster deductions only when these points hold:

• The property is used in a trade or business or held for the production of income.
• Each component is properly classified under the asset class rules and case law, with cost support.
• For 100% bonus depreciation, the property was acquired after January 19, 2025 (for purchased property, generally the date of a written binding contract) and meets the other §168(k) requirements.
• Used property is eligible only if the taxpayer did not previously use it and did not acquire it from a related party.
• For a building placed in service in an earlier year, missed depreciation is generally claimed through an accounting method change on Form 3115.

How it works

After acquisition, the study allocates cost among land (not depreciable), the building shell, and shorter-lived components. The components go on Form 4562 with their own lives, and bonus depreciation applies to eligible components unless you elect out by class. The remaining building cost is depreciated on the straight-line method with a mid-month convention.

The benefit depends on whether you can use the deduction. For most rental owners, rental losses are passive and can offset only passive income unless an exception applies, such as real estate professional status or the short-term rental rules. The excess business loss limit under IRC §461(l), which OBBBA made permanent, can also defer part of a large loss.

Studies cost money, and their value depends on the building's cost, how long you will hold it, your tax rates now and later, and whether a partial disposition or repair election could add further benefits.

Timing also matters for improvements. Qualified improvement property, meaning certain interior improvements to nonresidential buildings placed in service after the building, is 15-year property that can qualify for bonus depreciation. Section 179 expensing may be available for some of the same components, subject to its own dollar and income limits. If you replace components that were separately identified in a study, a partial disposition election can let you deduct the remaining basis of the old component rather than depreciating two roofs or two HVAC systems at once.

Risks and IRS scrutiny

Examiners review whether the study's methods and allocations are supported, whether items classified as personal property are really structural components, and whether bonus depreciation rules and dates were applied correctly. Poorly supported studies can lead to adjustments and accuracy-related penalties.

When you sell, depreciation on reclassified personal property is recaptured as ordinary income, and depreciation on the building is taxed at up to 25% as unrecaptured section 1250 gain. A like-kind exchange may defer this in some cases.

Who it is not for

Cost segregation often does not pay for smaller properties where the study fee exceeds the value of accelerating deductions, for owners who plan to sell soon, and for owners whose losses would be suspended under the passive activity rules with no passive income to absorb them. It is also less valuable when current tax rates are expected to be lower than rates at sale.

How ebotCPA helps

We estimate the potential reclassification, confirm acquisition dates and bonus eligibility, test whether you can use the deductions, coordinate with a qualified study provider, and handle the depreciation reporting or accounting method change.

Book a $497 Case Analysis to have Ebot Mbi, CPA, EA review your facts before you act.

Primary sources

1. 26 U.S.C. §168(c) and (k) (as amended by P.L. 119-21). Recovery periods and special depreciation allowance.

   Sets 27.5- and 39-year recovery periods and allows 100% bonus depreciation for qualified property acquired after January 19, 2025.

2. 26 U.S.C. §1245. Gain from dispositions of certain depreciable property.

   Recaptures depreciation on personal property as ordinary income on sale.

3. IRS Notice 2026-11. Interim guidance on additional first-year depreciation.

   Provides interim guidance on the January 19, 2025 acquisition-date rule and related elections.

4. Publication 5653. Cost Segregation Audit Techniques Guide.

   Describes how the IRS evaluates cost segregation studies.

5. 26 U.S.C. §469. Passive activity losses.

   Can limit use of accelerated depreciation from rental activities.

6. IRM 20.1.5. Return Related Penalties.

   Sets out how examiners assert the IRC §6662 accuracy-related penalty when a position is not supported.

Frequently asked questions