A cost segregation study has always been one of the more reliable ways for real estate owners to accelerate depreciation, but the math behind it shifted again under the One Big Beautiful Bill Act (OBBBA). With 100% bonus depreciation back on the table for qualifying property, the interaction between a cost segregation study and bonus depreciation now produces larger first-year deductions than the phase-down rules would have allowed. This article explains how the two provisions work together in 2026, what changed, and where owners should be cautious.
Quick answer: OBBBA permanently restored 100% bonus depreciation for qualified property with a recovery period of 20 years or less, acquired and placed in service after January 19, 2025. A cost segregation study reclassifies parts of a building into 5-, 7-, and 15-year property, and those reclassified components are exactly the assets that qualify for 100% bonus depreciation. The result: the components a study carves out can be fully expensed in year one rather than depreciated over decades, which sharply increases the immediate tax benefit.
What a Cost Segregation Study Does
A building bought or constructed for business or rental use is generally depreciated over a long horizon: 27.5 years for residential rental property and 39 years for nonresidential real property. That straight-line schedule spreads deductions thinly across decades, which delays the cash flow benefit owners care about most.
A cost segregation study breaks that single building cost into its parts. An engineering-based analysis identifies components that the tax law treats as personal property or land improvements rather than as part of the structure. Items such as carpeting, removable fixtures, decorative lighting, specialized electrical, and certain finishes can fall into 5- or 7-year property classes, while parking lots, sidewalks, landscaping, and exterior lighting often fall into the 15-year land improvement class.
By moving these components out of the 39-year (or 27.5-year) bucket and into shorter recovery periods, the owner accelerates deductions into the early years of ownership. The IRS treats this as a legitimate, well-established practice when the study is properly documented. The agency’s own Cost Segregation Audit Techniques Guide, published in February 2025, exists specifically to help examiners review these studies and sets out the elements of a quality study.
The mechanism matters because it determines who can defend the result. A study is not a simple percentage estimate applied to a purchase price. It is a documented allocation supported by construction records, cost data, and engineering judgment, tying each reclassified dollar to a specific building component and the asset class the tax law assigns to it. That documentation is what separates a sustainable position from one that collapses under examination.
How OBBBA Changed the Bonus Depreciation Math
Bonus depreciation lets a taxpayer deduct a percentage of the cost of qualifying property in the year it is placed in service, on top of regular MACRS depreciation. Under the Tax Cuts and Jobs Act, bonus depreciation was scheduled to phase down: 40% for property placed in service in 2025, 20% in 2026, and 0% thereafter. That schedule steadily eroded the front-loading benefit a cost segregation study could deliver.
OBBBA reversed that phase-down. The law permanently restores 100% bonus depreciation for most qualified property acquired and placed in service after January 19, 2025. Qualifying property generally means tangible property with a recovery period of 20 years or less, which is the category that captures the 5-, 7-, and 15-year assets a study produces.
This is where the two provisions reinforce each other. Without bonus depreciation, a study still accelerates deductions, but each reclassified component is depreciated over its 5-, 7-, or 15-year life. With 100% bonus depreciation in effect, those same components can be deducted in full in the first year. The study identifies the eligible property, and bonus depreciation expenses it immediately.
The difference is significant. Under a 40% bonus rate, an owner with several million dollars of reclassified components writes off less than half of that amount in year one. Under the restored 100% rate, the entire reclassified amount becomes a current deduction, subject to the usual limitations on losses and at-risk rules.
The word “permanently” carries real planning weight. During the phase-down years, owners faced pressure to act before the rate stepped down, and some shelved studies once the benefit looked like it was disappearing. A permanent 100% rate removes that artificial deadline and lets the decision turn on the economics of the property itself rather than on a closing window.
The Timing Rules That Decide Which Rate Applies
The January 19, 2025 line matters, and the acquisition date can be earlier than owners expect. For bonus depreciation purposes, the acquisition date is generally the date a written binding contract was entered into. Property under a binding contract signed before January 20, 2025 is treated as acquired on that contract date, which can push it into the older phase-down rules even if it was physically placed in service later.
In practice, this means property placed in service between January 1 and January 19, 2025, and property acquired on or before January 19, 2025, remains subject to the prior phase-down rates: 40% in 2025, 20% in 2026, and 0% afterward. Property that clears both the acquisition and placed-in-service tests after January 19, 2025 is eligible for the 100% rate.
For real estate, the placed-in-service date is usually when the property is ready and available for its intended use, which for a rental is typically when it is available to be leased. Owners planning a study should confirm both dates with their advisor before assuming the 100% rate applies. Pease Bell’s tax advisory services team can help map a specific acquisition to the correct rate.
Two transactions that look identical on the surface can land on opposite sides of the line. A building under contract in December 2024 and a building under contract in February 2025 may both close and open for business in the same month, yet only the second one qualifies for the 100% rate. Pinning down the binding-contract date early, before a study is commissioned, avoids building a tax plan on the wrong assumption.
A Simplified Example
Assume an investor buys a nonresidential building in mid-2026 with a $5,000,000 depreciable basis, placed in service after January 19, 2025, with no binding contract predating January 20, 2025. Without a study, the building depreciates over 39 years, producing roughly $128,000 of straight-line depreciation in a full first year.
Now assume a cost segregation study reclassifies $1,250,000 of that basis into 5-, 7-, and 15-year property. Because those components qualify for 100% bonus depreciation under OBBBA, the owner can deduct the full $1,250,000 in the first year, in addition to regular depreciation on the remaining building basis. The first-year deduction jumps from roughly $128,000 to well over $1,000,000.
These figures are illustrative. Actual reclassification percentages vary widely by property type, and the deductible loss in any year is limited by passive activity rules, at-risk limits, and the taxpayer’s overall tax situation. The point is the order of magnitude: pairing a study with 100% bonus depreciation can convert a modest first-year deduction into a substantial one.
What to Watch For
Accelerated deductions are not free money. They are a timing benefit, and the trade-offs deserve attention before an owner commits to a study.
Depreciation recapture is the main one. When the property is sold, the accelerated depreciation taken on personal property components can be recaptured as ordinary income under Section 1245, and gain attributable to real property depreciation is subject to unrecaptured Section 1250 treatment. The study front-loads deductions, but a portion of that benefit may come back at sale, potentially at higher rates.
State conformity is another. Not every state follows federal bonus depreciation, so the federal first-year deduction may not flow through to the state return. Owners with property in multiple states should model the state impact separately.
Finally, study quality controls audit risk. The IRS guidance sets out what a defensible study looks like, including the preparer’s qualifications and methodology. A poorly documented study invites scrutiny and can be unwound on examination. Real estate owners evaluating a study should work with advisors who understand both the engineering and the tax rules. Pease Bell’s real estate industry team works with property owners on exactly these decisions.
There is also a cash flow dimension that owners sometimes overlook. A large first-year deduction can create or enlarge a loss, but the value of that loss depends on having income to offset, either now or through carryforward. An owner with limited current taxable income may find the benefit deferred rather than realized in the year of the study, which changes the net present value calculation.
Who Benefits Most in 2026
The owners who gain the most from pairing a study with bonus depreciation generally share a few traits. They have meaningful taxable income to absorb the deductions, they expect to hold the property long enough that recapture at sale is acceptable, and they own property types with a high proportion of reclassifiable components, such as restaurants, hotels, retail centers, and certain manufacturing or medical facilities.
Owners of recently acquired or newly constructed property are obvious candidates, but a study can also be applied to property placed in service in prior years through a “look-back” study and a change in accounting method, which allows the catch-up depreciation to be claimed without amending returns. Whether that move pairs with bonus depreciation depends on when the property was originally placed in service.
The decision is rarely one-size-fits-all. It depends on income, holding period, entity structure, and state footprint. The reinstated 100% rate makes the upside larger than it was during the phase-down years, which is reason enough to revisit a study that may have been shelved when bonus depreciation was scheduled to disappear.
Frequently Asked Questions
Is bonus depreciation really back to 100% in 2026?
Yes. OBBBA permanently restored 100% bonus depreciation for qualified property with a recovery period of 20 years or less, acquired and placed in service after January 19, 2025. Property acquired under a binding contract signed before January 20, 2025, or placed in service earlier, may still fall under the old phase-down rules of 40% for 2025 and 20% for 2026.
Does a cost segregation study still help if bonus depreciation is 100%?
Yes, and arguably more than ever. Bonus depreciation only applies to property with a recovery period of 20 years or less. A study is what identifies and reclassifies building components into those shorter-lived classes, so it is the mechanism that makes the components eligible for the 100% deduction in the first place.
What happens to the deductions when I sell the property?
Accelerated depreciation can be recaptured at sale. Personal property components are generally subject to Section 1245 recapture as ordinary income, and depreciation on the real property is subject to unrecaptured Section 1250 rules. A study shifts deductions earlier, but a portion of the benefit can reverse at disposition, so the holding period and exit plan matter.
How much does a cost segregation study cost?
Fees vary by property size and complexity, and commonly fall in the range of several thousand to roughly $15,000 for smaller properties, with larger or more complex properties costing more. The right comparison is the fee against the net present value of the accelerated deductions, which an advisor can model before you commit.
The Bottom Line
A cost segregation study and bonus depreciation are two separate tools that work best together. The study reclassifies building components into 5-, 7-, and 15-year property, and OBBBA’s restored 100% bonus depreciation lets those components be expensed in full in year one for property that clears the post-January 19, 2025 acquisition and placed-in-service tests. The benefit is real but it is a timing benefit, with recapture, state conformity, and documentation all affecting the net result. Owners weighing a study in 2026 should confirm the applicable bonus rate for their specific property and model the after-sale picture before moving forward.
Sources: IRS Audit Techniques Guides (Cost Segregation ATG, 02/2025); IRS Cost Segregation Audit Techniques Guide, Publication 5653 (PDF).
