Cost segregation studies explained: how businesses accelerate depreciation

Most business owners and investors depreciate their commercial property as a single asset over 39 years, accepting a slow, fixed deduction schedule without realizing a better option exists. As Greg O'Brien, CPA at Anomaly CPA explains, cost segregation studies give property owners a legal, IRS-recognized method to reclassify building components into shorter asset lives, pulling significant deductions forward into the years when they create the most value. With the One Big Beautiful Bill Act permanently restoring 100% bonus depreciation after January 19, 2025, the impact of a well-executed cost segregation study has never been larger. This is foundational real estate tax strategy that every property-owning business should understand.

What cost segregation studies are - and why a building is not one asset

For tax purposes, a commercial building is not treated as a single, indivisible asset. It is a collection of systems and components with different functions, useful lives, and applicable depreciation schedules under the Modified Accelerated Cost Recovery System (MACRS).

Definition - IRC §168 establishes the MACRS depreciation system, which assigns recovery periods to different classes of property. Commercial real property depreciates over 39 years. Residential rental property depreciates over 27.5 years. Personal property and land improvements depreciate over 5, 7, or 15 years, depending on the asset classification.

A cost segregation study is an engineering-based analysis that identifies which components of a building qualify for shorter recovery periods under IRC §168. Electrical outlets dedicated to equipment, specialty flooring, interior fixtures, security systems, accent lighting, and land improvements such as parking areas and landscaping are among the components that can be reclassified from 39-year real property into 5-, 7-, or 15-year personal property categories. On average, 20% to 40% of a building's total cost can be reclassified.

Key takeaway: A building is a collection of components with different tax lives. Cost segregation studies identify which components qualify for accelerated depreciation and reclassify them accordingly under IRS rules.

How the reclassification process works

The IRS requires that cost segregation studies be conducted using an engineering-based methodology. A qualified engineer or construction cost specialist must physically inspect the property, review construction documents, and apply recognized cost-estimating techniques to each reclassified component.

For a full breakdown of the IRS Audit Techniques Guide (ATG), the 13 quality elements every compliant study must contain, and the documentation requirements that protect deductions at audit, see our detailed guide on IRS rules for cost segregation studies.

Components that remain at 39 years include the structural shell: load-bearing walls, the roof, elevators, HVAC systems serving the building as a whole, and the core electrical and plumbing infrastructure that serves structural functions. Components that qualify for reclassification include assets that serve a business function rather than a structural one.

Key takeaway: The engineering analysis distinguishes structural components from business-function components. Only the latter qualify for reclassification. Rule-of-thumb estimates without a site inspection do not satisfy IRS requirements.

How the One Big Beautiful Bill Act changed the cost segregation equation

Reclassifying components to shorter asset lives creates the opportunity to deduct them faster. Bonus depreciation determines how much faster.

Definition - IRC §168(k) allows taxpayers to immediately deduct a percentage of the cost of qualifying property in the year it is placed in service, rather than spreading deductions across the full recovery period. The One Big Beautiful Bill Act (OBBBA), signed into law on July 4, 2025, permanently restored 100% bonus depreciation for qualifying assets placed in service after January 19, 2025. (Source: OBBBA, Pub. L. No. 119-21, §70101.)

Before OBBBA, the bonus depreciation rate followed a declining schedule: 80% in 2023, 60% in 2024, and 40% during the first 19 days of January 2025. A property owner who identified $600,000 of qualifying personal property in early 2025 could deduct only $240,000 immediately. The same study completed after January 19, 2025, allows the full $600,000 to be deducted in year one. This is why cost segregation studies have become one of the most consequential tools in advanced tax strategy for property-owning businesses today. The reclassification creates eligible property - and 100% bonus depreciation immediately expenses it.

Key takeaway: Cost segregation and 100% bonus depreciation are a two-part mechanism. The study identifies qualifying components; bonus depreciation deducts them in year one. Without the study, the 39-year schedule applies regardless of the bonus rate.

Which businesses and property types qualify

Cost segregation studies are not exclusive to real estate investors. Any business that owns, constructs, acquires, or significantly renovates commercial or income-producing real property is a candidate.

Eligible property types include: commercial office buildings, retail centers, hotels, manufacturing facilities, warehouses, medical offices, multifamily properties, and tenant improvements made to leased space. The IRS also permits look-back studies on properties placed in service in prior years, without requiring amended tax returns.

Definition - A look-back study applies cost segregation principles to a property already in service. The cumulative catch-up deduction for all missed prior-year depreciation is claimed in a single tax year via Form 3115, Application for Change in Accounting Method, under the IRS automatic consent procedures. No amended returns are required.

As a general threshold, properties with a depreciable basis of $500,000 or more generate savings that clearly justify the cost of the study, which typically ranges from $5,000 to $15,000. Smaller properties may still qualify depending on their composition and the marginal tax rate of the owner. (Source: IRS Publication 946, How to Depreciate Property.)

Key takeaway: Any business owning qualifying commercial real property - including properties placed in service in prior years - is a candidate. The $500,000 threshold is a practical starting point for evaluating whether study costs are justified by expected savings.

What the tax savings actually look like

The financial impact of a well-executed cost segregation study is direct and measurable. The reclassified components generate deductions that reduce taxable income immediately, rather than incrementally over 39 years.

Worked example

A business acquires a $2 million commercial office building in 2026. Land accounts for $300,000 of the purchase price, leaving a depreciable basis of $1,700,000. Without a cost segregation study, the standard annual deduction is $43,590 ($1,700,000 divided by 39 years).

A cost segregation study identifies 30% of the depreciable basis - or $510,000 - as qualifying 5-, 7-, and 15-year personal property and land improvements. Under the 100% bonus depreciation rate restored by OBBBA, the entire $510,000 is deducted in year one.

The remaining $1,190,000 continues on the 39-year schedule, generating $30,513 in annual deductions. Total year-one depreciation with cost segregation: $540,513. Without the study: $43,590. At a 35% marginal tax rate, the cost segregation study generates approximately $174,000 in additional year-one tax savings - against a study cost of approximately $8,000.

Assumptions: 35% marginal tax rate. 30% reclassification rate applied to depreciable basis. 100% bonus depreciation applies to all reclassified personal property placed in service after January 19, 2025, per OBBBA. Land excluded from depreciable basis. Study cost approximately $8,000. (Based on anonymized Anomaly CPA client data, Q2 2025.)

Key takeaway: For a $2 million commercial property, a cost segregation study can generate more than $170,000 in net first-year tax savings at current bonus depreciation rates - a return that substantially exceeds the cost of the study itself.

When cost segregation studies do not make sense

Not every property owner benefits from a cost segregation study, and an advisor who recommends one without evaluation is not serving the client's best interest.

Three situations where the strategy typically does not produce the expected benefit: first, when the property owner plans to sell within two to three years and the depreciation recapture on reclassified components - taxed at ordinary income rates - erodes the upfront savings. Second, when the owner is in a consistent net operating loss position and additional deductions cannot offset taxable income. Third, when rental property losses are passive and the owner does not qualify as a real estate professional under IRC §469(c)(7), limiting their ability to use the deductions against ordinary income in the current year.

Key takeaway: A cost segregation study is a timing strategy, not a permanent tax elimination. Recapture, passive loss limitations, and holding period all affect the net benefit. Modeling the full picture before engaging a study firm is essential.

Action steps for business owners

● Identify every commercial or income-producing property you own, including properties acquired in prior years, as candidates for a cost segregation study or look-back study via Form 3115.

● Confirm that any study you commission is prepared by a qualified engineer with a documented site inspection - not a rule-of-thumb allocation from a non-engineering vendor.

● Model the depreciation recapture impact before starting the study, particularly if you anticipate selling the property within five years.

● Confirm whether you qualify as a real estate professional under IRC §469(c)(7), since passive loss rules significantly affect how much of the accelerated deduction you can use against ordinary income.

● Contact Anomaly CPA to assess which of your properties qualify, model the year-one and multi-year tax impact under current 100% bonus depreciation rates, and ensure the study is prepared by the same team that signs and defends your return.

Book a call with the Anomaly CPA team to model the full cost segregation impact on your portfolio and build a strategy that holds up long after the first-year deduction is taken.

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