If you own commercial real estate and you’ve been depreciating your building over 39 years, you’re almost certainly leaving substantial tax savings on the table. A cost segregation study can reclassify 20-40% of your property’s basis into shorter recovery periods — 5, 7, or 15 years — and with the OBBBA’s permanent restoration of 100% bonus depreciation, that reclassified property is fully deductible in the first year.
For a $5 million commercial property, that often translates to $1 million or more in first-year deductions rather than spreading them across decades. At a 35% tax rate, that’s around $350,000 in immediate tax savings — cash that goes back into the business or the next acquisition.
But how does a cost segregation study actually work? What does the process look like from engagement to deduction? And what’s changed in 2025-2026 that makes this strategy more powerful than ever? Here’s the complete breakdown.
Key Takeaways
- A cost segregation study typically reclassifies 20-40% of a commercial property’s basis from 39-year recovery into 5-, 7-, or 15-year property eligible for bonus depreciation
- The OBBBA permanently restored 100% bonus depreciation for qualifying property acquired and placed in service after January 19, 2025 — both contract date and placed-in-service date matter
- For a $5 million commercial property, accelerated deductions typically generate $300,000-$500,000 in immediate tax benefits at typical tax rates
- Cost segregation can be applied retroactively using Form 3115 — no need to amend prior returns to capture missed deductions on properties placed in service in earlier years
What Is a Cost Segregation Study?
A cost segregation study is an IRS-recognized engineering-based tax strategy that identifies and reclassifies components of a commercial property into shorter MACRS (Modified Accelerated Cost Recovery System) recovery periods. Instead of depreciating an entire building over 39 years (commercial) or 27.5 years (residential rental), specific components — flooring, lighting, specialized electrical, plumbing fixtures, decorative finishes, land improvements — get reclassified into 5-, 7-, or 15-year property categories.
The IRS doesn’t create new deductions through cost segregation. The same total depreciation is taken. But it shifts deductions forward in time, dramatically improving cash flow through the time value of money. And under current law, the reclassified property qualifies for 100% bonus depreciation, meaning the entire reclassified amount is deductible in year one.
The MACRS Categories: Where the Savings Come From
The IRS classifies depreciable property into specific recovery periods under MACRS. Without a cost segregation study, a commercial building defaults to a 39-year recovery period for the entire structure. With a study, components are reallocated to their proper categories:
The key insight: Property with a recovery period of 20 years or less qualifies for 100% bonus depreciation under the OBBBA. That includes 5-, 7-, and 15-year property — but not the 27.5-year or 39-year structural categories. The whole purpose of cost segregation is to identify everything that can move out of the long recovery periods and into the bonus-eligible categories.
The OBBBA: Why Cost Segregation Is More Valuable Than Ever
2025 Legislative Update
Before the OBBBA, bonus depreciation was on a phasedown trajectory: 60% in 2024, 40% in 2025, 20% in 2026, and complete elimination in 2027. The OBBBA, signed July 4, 2025, permanently restored 100% bonus depreciation for qualifying property — reversing the entire phasedown.
OBBBA Cost Segregation Provisions
100% bonus depreciation — permanent
Qualifying property acquired and placed in service after January 19, 2025 qualifies for 100% bonus depreciation. Both the binding contract date and the placed-in-service date must fall after this date. Property with contracts signed before January 20, 2025 receives only 40% bonus even if placed in service later.
Section 179 doubled to $2.5M (2025), $2.56M (2026)
Section 179 limit increased from $1.25 million to $2.5 million for 2025, with a phaseout threshold of $4 million. For 2026, the limit is $2.56 million with a $4.09 million phaseout. Especially valuable for property types not eligible for bonus depreciation, like certain roofs and HVAC.
Qualified Production Property (QPP) — new deduction
Section 168(n) allows 100% expensing of certain nonresidential real property used in qualified production activities (manufacturing, refining, agricultural processing). Construction must begin between January 20, 2025 and December 31, 2028, and the property must be placed in service before January 1, 2031.
The contract date trap: The OBBBA’s January 19, 2025 cutoff is unusually strict — both the contract signing date and the placed-in-service date must fall after that date for 100% bonus to apply. A property placed in service on January 22, 2025 with a contract signed in December 2024 receives only 40% bonus. The same property with a contract signed January 21, 2025 gets 100% bonus. On a $5M property with $1M of bonus-eligible components, that’s the difference between a $400K first-year deduction and a $1M first-year deduction. If you’re acquiring property near the cutoff, the contract date is everything.
The Step-by-Step Cost Segregation Process
Here’s what the engagement actually looks like from start to finish, broken into the six phases we follow at Tax Formulations.
Feasibility Analysis
Before any engagement begins, we evaluate whether a study makes economic sense. We review the property type, depreciable basis, ownership structure, holding period intent, and tax position. We provide an estimated benefit range — and if the projected savings don’t justify the study fee, we tell you. Most studies yield 10-20x ROI, but some don’t, and you should know upfront.
Document Collection
We collect available documentation: closing statements, construction draw schedules (for new builds), AIA pay applications, blueprints and as-builts, building plans, MEP drawings, change orders, owner-supplied equipment lists, and prior depreciation schedules. The more documentation available, the more granular and defensible the study.
Site Inspection
An engineer physically inspects the property. They photograph and document each major building component — interior finishes, lighting, electrical panels, plumbing, HVAC, kitchen equipment, security systems, parking, landscaping, signage. The IRS’s Audit Techniques Guide treats engineer-led site inspections as the gold standard for defensible studies.
Engineering Cost Allocation
Engineers and tax specialists analyze the documentation and inspection findings to allocate costs to MACRS categories. This involves applying engineering principles, IRS guidance (including the §1245 vs §1250 distinction), and current case law. For new construction, allocations are based on actual construction cost data. For acquisitions, allocations use construction cost estimating methodology.
Report Preparation
We deliver a comprehensive engineering report documenting the methodology, asset classifications, supporting calculations, photographs, and IRS-recognized basis for each reclassification. The report becomes part of your tax records and serves as your audit defense file. A quality report is meticulously documented to withstand IRS scrutiny.
Tax Filing Coordination
For current-year studies, the results flow directly into your tax return through Form 4562. For retroactive “look-back” studies on prior-year acquisitions, we file Form 3115 (Application for Change in Accounting Method) to claim the cumulative catch-up depreciation in the current year — without amending prior returns. We work directly with your CPA throughout.
Real Example: $5M Office Building Cost Segregation
Here’s how the math plays out for a typical commercial office building acquired in 2025 for $5 million ($4.5M building basis after land allocation), with a contract signed and property placed in service after January 19, 2025.
The bottom line on this example: Without a cost segregation study, you’d take roughly $115,000 in first-year depreciation. With a study, you’d take roughly $1.21 million. At a 35% effective tax rate, that’s approximately $385,000 in additional first-year tax savings. The cost of the study is typically $5,000-$15,000. ROI is often 25-50x in the first year alone.
Retroactive Studies: Capturing Missed Deductions on Older Properties
One of the most underutilized opportunities in cost segregation is the “look-back” or retroactive study. If you acquired a commercial property in a prior year and never had a cost segregation study performed, you can still claim the missed depreciation — without amending prior returns.
The mechanism is Form 3115 (Application for Change in Accounting Method). You file the form with your current-year tax return, electing a §481(a) adjustment that captures all the cumulative depreciation you should have taken under proper classification — and deducts it in the current year. The IRS treats this as an automatic change in accounting method, so no IRS approval is required.
From our practice: The look-back opportunity is most valuable for properties acquired in 2017-2024, when bonus depreciation was at 100% under TCJA before phasing down. A property acquired in 2020 that should have had cost segregation done at the time can still capture those bonus deductions today through Form 3115 — and the catch-up adjustment lands in the current year, when you can use it. We routinely see retroactive studies generate larger first-year tax savings than current-year studies on similar properties.
What Property Types Are Best for Cost Segregation?
Cost segregation works for virtually any commercial or income-producing real estate, but some property types yield significantly higher percentages of reclassifiable basis than others. Here’s a general guide:
Own Commercial Real Estate? Let’s Run the Numbers.
We’ll provide a free feasibility analysis on any commercial property — current acquisition or older property. You’ll see the projected first-year tax savings before any engagement begins. If the numbers don’t justify a study, we’ll tell you.
Frequently Asked Questions
How much does a cost segregation study cost?
Fees typically range from $5,000 to $15,000 for commercial properties, depending on size, complexity, and documentation availability. Larger or more complex properties (manufacturing facilities, hospitals, hotels) cost more. Smaller residential rental properties may be eligible for less expensive “desktop” studies. The fee is almost always dwarfed by the first-year tax savings — typical ROI is 10-50x.
Can I do a cost segregation study on a property I bought years ago?
Yes. A retroactive or “look-back” study captures missed depreciation on prior-year acquisitions through Form 3115. The cumulative §481(a) catch-up adjustment is deducted entirely in the current year — no amended returns needed. This is one of the most valuable opportunities for property owners who never had a study performed at acquisition.
What about depreciation recapture when I sell?
Yes — accelerated depreciation creates depreciation recapture exposure on sale. Section 1245 property (5- and 7-year) is recaptured at ordinary income rates. Section 1250 property (15-year and longer) is recaptured at up to 25%. However, the time value of money usually still favors cost segregation, especially with longer holding periods. A 1031 exchange can defer all recapture by rolling proceeds into a like-kind replacement property.
Does cost segregation work for residential rental property?
Yes. The residential structure itself depreciates over 27.5 years (not eligible for bonus), but a cost segregation study identifies appliances, flooring, fixtures, landscaping, and other components that can be reclassified into 5-, 7-, or 15-year property eligible for 100% bonus depreciation. Apartment buildings and short-term rental properties (under specific rules) often see substantial benefits.
Will a cost segregation study trigger an IRS audit?
A properly performed engineering-based cost segregation study does not increase audit risk — it’s an IRS-recognized strategy, and the IRS publishes its own Audit Techniques Guide on cost segregation. The risk comes from poorly executed studies that lack engineering rigor or use aggressive allocations. A defensible study with full documentation, site inspection, and proper methodology stands up to scrutiny. Read our cost segregation overview for more on the IRS-recognized approach.
What Should You Do Next?
If you own commercial real estate — whether you acquired it last month or ten years ago — and you’ve never had a cost segregation study performed, you should at least know what the projected savings would be. The feasibility analysis is free, and the numbers tell the story.
The OBBBA has made this strategy more powerful and more permanent than at any time in the last decade. Pair it with the R&D tax credit if you’re using the property for engineering or development work, or with QPP if it’s a manufacturing facility.
Schedule a free consultation and we’ll evaluate your property’s potential. We work with property owners across California and nationwide.
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Martin Gamez
Founder, Tax Formulations
Martin is a tax credit specialist with over 25 years of experience in federal and state R&D tax credits, cost segregation, and business tax incentives. His background includes tenure at Big Four and Top 10 accounting firms, with clients spanning technology, manufacturing, aerospace, engineering, construction, real estate, and life sciences. Read full bio →