Cost Segregation Study: How It Accelerates Depreciation

October 21, 2026 · George Beall

A cost segregation study is an engineering-based tax analysis that breaks a commercial or investment building into its individual components and reclassifies qualifying assets into shorter depreciation lives under the Modified Accelerated Cost Recovery System (MACRS). Instead of depreciating an entire structure over 27.5 or 39 years, owners deduct a meaningful portion of that cost in far fewer years, often in year one when 100% bonus depreciation applies. The result is a larger deduction now, a lower tax bill now, and improved cash flow for reinvestment.

What Is a Cost Segregation Study and How Does It Work?

When you purchase, construct, or renovate a building, federal tax law assigns the entire structure to a single long-lived asset class: 39 years for nonresidential property, or 27.5 years for residential rental. A cost segregation study challenges that default by identifying the components of the building that qualify for a shorter recovery period under IRC Section 168 and MACRS.

A qualified engineer or CPA-led team inspects the property, reviews construction blueprints and contractor invoices, and allocates costs to specific building components. Each component is then mapped to the appropriate MACRS asset class. Components that qualify for 5-, 7-, or 15-year recovery periods are separated from the structural shell, allowing the owner to depreciate them much faster than the base building.

The MACRS Asset Classes That Drive Acceleration

Cost segregation targets three shorter-life categories:

5-year property: Carpeting, certain electrical outlets and specialty wiring, decorative lighting fixtures, specialized plumbing, and other personal property embedded in the building.
7-year property: Office furniture built into common areas, certain removable equipment and fixtures.
15-year property: Land improvements such as parking lots, sidewalks, fencing, landscaping, exterior lighting, and storm drainage systems.

Most reclassified 5- and 7-year components are treated as Section 1245 personal property, while 15-year land improvements remain Section 1250 real property. Both categories allow accelerated deductions relative to the building shell. The structural building envelope, the roof, load-bearing walls, and HVAC serving the entire building typically remain in the 27.5- or 39-year class.

On average, industry experience suggests 20% to 35% of a building’s depreciable cost basis can be reclassified into shorter-lived categories, though the share varies significantly by property type. Restaurants, manufacturing plants, and hospitality properties tend to land at the higher end; straightforward office buildings at the lower end.

The Impact of Bonus Depreciation Under the OBBBA

The mechanics of cost segregation changed substantially when the One Big Beautiful Bill Act (OBBBA) was signed on July 4, 2025. The OBBBA permanently restored 100% first-year bonus depreciation for qualified property acquired and placed in service on or after January 19, 2025, with no scheduled phase-down.

Before the OBBBA, bonus depreciation had been stepping down from 100% (which applied through 2022 under the Tax Cuts and Jobs Act) toward 0% by 2027. That phase-down created uncertainty for buyers timing acquisitions. The permanent restoration removes that timing risk.

How Bonus Depreciation Amplifies Cost Segregation

Bonus depreciation under IRC Section 168(k) applies to MACRS property with a recovery period of 20 years or less. Every component reclassified by a cost segregation study into a 5-, 7-, or 15-year class qualifies. That means, for property meeting the post-January 19, 2025 acquisition test, those reclassified components can be deducted in full in the year placed in service.

Here is a simplified example. Suppose you acquire a $3 million office building (excluding land) and a cost segregation study identifies $750,000, or 25% of basis, as shorter-lived components. Under the default approach, you would depreciate the full $3 million over 39 years, generating roughly $77,000 per year. With cost segregation and 100% bonus depreciation applied to the $750,000, you deduct that entire amount in year one, plus the first year of straight-line depreciation on the remaining $2.25 million building, accelerating substantial tax savings into the period when you need cash the most.

Section 179 as a Complement

Section 179 expensing is another tool that can work alongside cost segregation for certain property types. For 2026, the Section 179 deduction limit is $2,560,000, with a phase-out beginning at $4,090,000 of qualifying property placed in service during the year. Because Section 179 is capped and cannot create or increase a net operating loss (while bonus depreciation can), most advisors apply bonus depreciation first to reclassified real property components and reserve Section 179 for equipment or other personal property. The two strategies can complement each other; understanding the interaction requires a detailed analysis of your specific situation.

Who Should Commission a Cost Segregation Study?

A cost segregation study makes economic sense when the tax benefit exceeds the cost of the study. That calculation depends on your tax rate, your depreciable basis, and whether passive activity rules or the at-risk rules allow you to actually use the deductions.

Generally, a study is worth pursuing when:

The building’s depreciable basis (excluding land) is $500,000 or more for commercial property.
You have taxable income to absorb the accelerated deductions, or you qualify as a real estate professional under IRC Section 469(c)(7) or have passive income to offset.
You own the property for the purpose of trade or business, or as an investment.
You have acquired, constructed, or substantially renovated the building recently, or you have owned property for years without having done a study (a lookback study can capture missed deductions).

Property types that tend to generate meaningful reclassification opportunities include retail centers, hotel and hospitality properties, manufacturing and industrial facilities, medical offices, restaurants, and multifamily residential complexes. Standard single-tenant office space generally yields a lower reclassification percentage, though a study may still be worthwhile depending on basis size.

Lookback Studies: Capturing Missed Deductions on Existing Property

You do not need to have purchased the building recently to benefit. If you have owned commercial property for years without a cost segregation study, a lookback analysis under the IRS’s automatic accounting method change procedures allows you to claim the cumulative catch-up depreciation in a single year without amending prior returns. This is done by filing Form 3115, Application for Change in Accounting Method, which generates a Section 481(a) adjustment. The controlling list of automatic changes is updated annually; as of 2026 it is Revenue Procedure 2025-23, which succeeded the earlier Revenue Procedure 2024-23.

IRS Documentation Standards

The IRS published its Cost Segregation Audit Techniques Guide (Publication 5653, most recently updated February 2025) to set expectations for what a defensible study looks like. The guide identifies 13 principal elements that examiners evaluate, including:

The qualifications of the preparer
The methodology used and its consistency with IRS-approved approaches
Support for all cost allocations tied to actual contractor invoices or industry-standard estimating data
Clear documentation of placed-in-service dates
Accurate legal descriptions and physical inspection evidence
Classification supported by the appropriate MACRS asset class and legal authority

The IRS favors the detailed engineering approach, which ties every dollar of reclassification to a specific component supported by contemporaneous construction records, blueprints, and invoices. Studies built on rules of thumb or rough estimates carry greater audit risk. See IRS Publication 5653 for the full guide.

Qualified preparers typically include licensed engineers with real property cost experience, or CPAs who work alongside engineers and have specific training in MACRS classification. The combination of engineering knowledge and tax expertise is what distinguishes a defensible study from a simple estimate.

Depreciation Recapture: The Trade-Off to Model Before You Commit

Accelerating depreciation into early years does not eliminate tax; it defers it. When you sell the property, the IRS recaptures the benefit through two mechanisms:

Section 1245 recapture: Applies to personal property (the 5- and 7-year components). All prior depreciation on these assets is recaptured as ordinary income at rates up to 37%.
Unrecaptured Section 1250 gain: Applies to real property, including the building shell and the 15-year land improvements, to the extent of depreciation that does not exceed straight-line. This portion is taxed at a maximum rate of 25%, higher than the top long-term capital gains rate. Any accelerated depreciation on 15-year property above the straight-line amount can be recaptured as ordinary income under Section 1250, though the straight-line MACRS method used for 15-year land improvements generally limits this exposure.

The net result is that recapture taxes are owed at sale, reducing the benefit of earlier deductions. Whether cost segregation delivers a positive net present value depends on your tax rate in the year of deduction, your expected rate at sale, how long you hold the property, and the time value of money. In most holding scenarios where the owner is in a high marginal rate and holds the property five years or more, the present-value benefit of early deductions outweighs the recapture cost, but the math is specific to each situation and should be modeled before commissioning a study.

A 1031 like-kind exchange at sale can defer recognition of both Section 1245 recapture and Section 1250 gain by rolling the proceeds into qualifying replacement real property, provided the 45-day identification and 180-day closing requirements are met.

The Study Process: What to Expect

A cost segregation study typically follows these steps:

Engagement and data gathering: The preparer collects purchase documents, construction contracts, cost certifications, and architectural drawings.
Site inspection: A qualified engineer walks the property, photographs components, and documents conditions.
Cost allocation: Using actual invoices or industry-standard cost estimating databases, the preparer allocates the total depreciable basis to each component.
MACRS classification: Each component is assigned to the correct asset class based on its function and the relevant statutory authority.
Report delivery: The final report documents every allocation, the methodology, the authorities relied upon, and the resulting depreciation schedule.

Turnaround time is typically four to eight weeks for a standard commercial property, depending on the complexity of the building and the availability of construction records. Fee structures vary; most studies are priced on a fixed-fee basis related to property type and size, commonly ranging from $5,000 to $15,000 for mid-market commercial assets. (Industry estimate, not a codified rule.)

For businesses working with Modus’s tax advisory team, the study is integrated into a broader tax planning conversation that considers entity structure, passive activity rules, alternative minimum tax exposure, and exit strategy before any engagement begins.

Coordinating Cost Segregation with Your Broader Tax Plan

Cost segregation is most effective when it is coordinated with other planning, not commissioned in isolation. Key integration points include:

Passive activity rules: Deductions from rental real estate are generally passive and can only offset passive income unless the taxpayer qualifies as a real estate professional or the property meets the short-term rental exception.
At-risk rules: Deductions are limited to the amount the taxpayer has at risk in the activity.
AMT: Individual owners should review whether accelerated depreciation triggers alternative minimum tax, though the OBBBA made permanent changes that reduced AMT exposure for many taxpayers.
State conformity: Many states do not conform to federal bonus depreciation rules, which means you may owe state taxes in year one on income that was shielded federally.
Exit planning: The recapture analysis discussed above should be modeled for your expected holding period and exit strategy before committing to accelerated deductions.

The advisory team at Modus works through these variables systematically, using tax modeling that accounts for both the federal and state picture before a study is commissioned.

See also the IRS’s guidance in Publication 946, How to Depreciate Property and the underlying authority in 26 CFR 1.168(k)-2-2) for the regulatory framework governing bonus depreciation. Note that the Treasury regulations still reflect the pre-OBBBA phase-down schedule and have not yet been updated for the permanent 100% rate enacted in 2025.

Frequently Asked Questions

What is a cost segregation study?

A cost segregation study is an engineering-based tax analysis that identifies building components qualifying for shorter depreciation lives under MACRS, typically 5, 7, or 15 years, rather than the standard 27.5 or 39 years for the building as a whole. The result is accelerated depreciation deductions that reduce taxable income in earlier years.

How much can a cost segregation study save in taxes?

The savings depend on your marginal tax rate, the size and type of the building, and the percentage of costs that can be reclassified. For a $2 million commercial building with 25% reclassified and 100% bonus depreciation applied, the study might generate $500,000 in first-year deductions rather than spreading that amount over 39 years. At a 35% effective rate, that can represent more than $170,000 of deferred tax in year one alone. Individual results vary and the savings must be weighed against eventual recapture taxes.

Does 100% bonus depreciation still apply in 2026?

Yes. The One Big Beautiful Bill Act (OBBBA), signed July 4, 2025, permanently restored 100% bonus depreciation for qualified property acquired and placed in service on or after January 19, 2025. There is no longer a scheduled phase-down. This applies to MACRS property with a recovery period of 20 years or less, which includes all components reclassified by a cost segregation study.

Can I do a cost segregation study on property I have owned for years?

Yes. A lookback study allows you to claim accumulated catch-up depreciation on property you have owned without a prior study. The deduction is taken in a single year by filing Form 3115 under the IRS’s automatic accounting method change procedures, without amending prior-year returns. This can generate a substantial deduction even on long-held property.

What is depreciation recapture and how does it affect cost segregation?

When you sell a property, the IRS taxes previously deducted depreciation as ordinary income (for Section 1245 personal property, at rates up to 37%) or as unrecaptured Section 1250 gain (for real property, capped at 25%). Because cost segregation accelerates depreciation into earlier years, it increases the amount subject to recapture at sale. This is a timing benefit, not a permanent tax elimination, so the economics depend on holding period, marginal rates, and whether a 1031 exchange is used at exit.

Who should prepare a cost segregation study?

A defensible study should be prepared by a qualified engineer with experience in real property cost analysis, often working alongside a CPA with MACRS expertise. The IRS Cost Segregation Audit Techniques Guide (Publication 5653) specifies that preparer qualifications are one of the 13 elements examiners evaluate in an audit. Studies built on estimates without engineering support or construction-cost documentation carry higher audit risk.

Filed under: Business Tax & Credits