Cost segregation studies: the §1245 / §1250 reallocation framework, the engineering-based study requirement, the 100% bonus depreciation restoration under OBBBA, and the depreciation recapture trade-off
A cost segregation study is an engineering analysis that reallocates the depreciable basis of a real estate purchase or significant renovation among multiple depreciation categories. Without the study, the entire building cost defaults to either 27.5-year residential rental treatment under §168(c) or 39-year nonresidential commercial treatment, both as §1250 real property. With the study, components that qualify as §1245 personal property (carpeting, removable cabinetry, decorative lighting, dedicated electrical for business equipment, specialty plumbing for business use) get reallocated to 5-year or 7-year recovery periods, and components that qualify as §1250(c) land improvements (parking lots, sidewalks, landscaping, exterior lighting, signage) get reallocated to 15-year recovery.
The financial impact is substantial. A $5 million commercial property that defaults to 39-year depreciation generates roughly $128,000 per year of depreciation deduction. The same property with a cost segregation study reallocating 30% of basis to 5/7/15-year categories generates substantially more deduction in the first several years, particularly when combined with §168(k) bonus depreciation. For real estate investors with substantial properties or material income to absorb the deductions, the study often pays for itself many times over in the first year.
The framework was substantially affected by the One Big Beautiful Bill Act (OBBBA) signed July 4, 2025, which permanently restored 100% bonus depreciation for qualified property placed in service on or after January 20, 2025. The 2017 TCJA bonus depreciation had been phasing down (60% for 2024, 40% for 2025, 20% for 2026); the OBBBA restoration eliminates the phase-down and makes 100% bonus depreciation a stable planning assumption for the foreseeable future.
What is the legal framework for cost segregation studies?
The legal framework rests on the §1245/§1250 distinction in the Internal Revenue Code, the Tax Court's 1997 Hospital Corporation of America decision applying investment tax credit rules to classify property, and the IRS Cost Segregation Audit Techniques Guide (Publication 5653), which establishes 13 quality elements for defensible studies.
The statutory authority for the §1245 vs §1250 distinction is the Code itself, but the operational framework for cost segregation studies has been shaped by case law and IRS administrative guidance.
The seminal case is Hospital Corporation of America v. Commissioner, 109 T.C. 21 (1997), where the Tax Court applied pre-1981 investment tax credit (ITC) rules to distinguish §1245 personal property from §1250 real property. The IRS acquiesced to the HCA decision in 1999, and the ITC framework became the operational test for §1245 / §1250 classification.
The IRS Cost Segregation Audit Techniques Guide (ATG), most recently updated in Publication 5653, provides the operational framework that examiners use to evaluate cost segregation studies. The ATG identifies 13 specific quality elements that a defensible study should include, lists preferred and disfavored methodologies, and provides examples of properly classified vs. improperly classified components.
What does §1245 vs §1250 mean in cost segregation?
Section 1245 personal property (carpeting, decorative lighting, dedicated electrical systems, movable partitions) qualifies for 5-year or 7-year accelerated depreciation recovery. Section 1250 real property (building shell, structural components, integrated HVAC) depreciates over 27.5 or 39 years. Section 1250(c) land improvements such as parking lots and sidewalks recover over 15 years.
The §1245 / §1250 distinction comes from the depreciation recapture provisions, but in cost segregation context, it operates as the dividing line between accelerated-recovery property and slow-recovery property.
§1245 personal property includes tangible personal property used in a trade or business, plus certain other property specified in §1245(a)(3). For real estate components, §1245 typically reaches:
Office furniture, fixtures, and equipment that are not structural components of the building.
Decorative elements (special wall coverings, decorative lighting that does not provide general illumination, decorative millwork that is not structural).
Dedicated electrical, plumbing, or mechanical systems serving specific business equipment (process piping, dedicated power for manufacturing equipment).
Carpeting, removable flooring, and similar components not integral to the building structure.
Movable partitions that are not load-bearing.
Specialty cabinetry and millwork in retail, restaurant, or medical environments.
Recovery periods for §1245 property are 5 years (most equipment), 7 years (office furniture), or other specified periods depending on the asset class under Rev. Proc. 87-56.
§1250 real property is buildings and their structural components: the building shell, structural elements, foundation, integrated HVAC for general building climate control, integrated electrical for general illumination, plumbing for general use, integrated security and fire suppression. Recovery period is 27.5 years for residential rental property or 39 years for nonresidential commercial property.
§1250(c) land improvements are improvements to land that are §1250 property but eligible for 15-year recovery: parking lots, sidewalks, landscaping, fencing, exterior lighting, signage. These are real property for purposes of the §1250 character analysis but get shorter recovery than the building shell.
What components typically get reallocated in a cost segregation study?
A typical commercial cost segregation study reallocates 10 to 15% of basis to 5-year §1245 property, 3 to 7% to 7-year §1245 property, and 10 to 20% to 15-year land improvements, leaving 60 to 77% in the 27.5-year or 39-year building category. Exact percentages vary by property type and building use.
A typical cost segregation study on a commercial property might reallocate the following:
| Category | Typical % of Basis | Recovery Period | Examples |
|---|---|---|---|
| §1245 personal property | 10-15% | 5 years | Carpeting, decorative lighting fixtures, removable cabinetry, dedicated electrical/mechanical serving specific business equipment |
| §1245 personal property | 3-7% | 7 years | Office furniture, fixtures, and equipment that are part of the original purchase price |
| §1250(c) land improvements | 10-20% | 15 years | Parking lots, sidewalks, exterior lighting, landscaping |
| §1250 real property (remainder) | 60-77% | 39 years (or 27.5 years residential) | Building shell, structural components, integrated HVAC, general electrical, general plumbing |
The exact reallocation depends on the property type. Manufacturing facilities and medical buildings tend to have higher §1245 percentages because of specialized equipment-serving systems. Office buildings tend to have moderate reallocations. Apartment buildings and standard residential rental tend to have lower §1245 percentages because most components are integrated structural components of the building.
The ATG specifically cautions against "rule of thumb" reallocations (e.g., applying a flat 20% reduction to building basis as personal property without supporting analysis). These approaches do not meet the engineering-based study requirement and are vulnerable to disallowance on audit.
What methodologies does the IRS require for cost segregation studies?
The IRS Audit Techniques Guide ranks cost segregation methodologies by reliability. Detailed engineering from actual construction records is the gold standard. Estimated engineering approaches and contractor surveys are also acceptable. Rule-of-thumb flat-percentage allocations are explicitly disfavored and unlikely to survive audit scrutiny.
The ATG identifies several acceptable methodologies, ranked roughly by IRS preference:
| Methodology | Description | IRS Preference |
|---|---|---|
| Detailed engineering from actual records | Uses construction invoices, contractor accounting records, and architect/engineer drawings to directly identify the cost of each component. Available primarily for newly constructed or recently renovated properties. | Gold standard (highest) |
| Detailed engineering cost estimate approach | Uses estimated costs from industry pricing databases (RSMeans, Marshall & Swift) rather than actual cost records. Engineering analysis still drives classification. | High (preferred when actual records unavailable) |
| Survey or letter approach | Asks the original contractor or developer for cost breakdowns. Less rigorous than engineering approaches. | Acceptable when properly documented |
| Residual estimation approach | Estimates the cost of certain components by subtracting other identified costs from the total. Used in combination with another methodology. | Acceptable as supplement only |
| Rule of thumb approach | Flat-percentage allocations not supported by engineering analysis. | Explicitly disfavored; unlikely to survive audit |
A "quality cost segregation report" per the ATG must include the methodology used, the basis for cost allocations, supporting documentation, qualifications of the preparer, and the specific component-by-component reallocation analysis.
How does cost segregation interact with bonus depreciation?
Cost segregation identifies property eligible for shorter recovery periods, and §168(k) bonus depreciation then allows immediate expensing of those reallocated amounts. The OBBBA permanently restored 100% bonus depreciation for property placed in service on or after January 20, 2025, fully restoring the value of cost segregation studies to their 2017 to 2022 peak.
§168(k) bonus depreciation allows immediate expensing of a percentage of qualified property in the year placed in service. The interaction with cost segregation is substantial: cost segregation identifies §1245 property and shorter-life §1250(c) property; bonus depreciation then allows immediate expensing of much of that reallocated amount.
The history of the bonus depreciation rate:
2017 (post-TCJA): 100% for qualified property placed in service after September 27, 2017.
2018-2022: 100% (TCJA framework continued).
2023: 80% (phase-down began).
2024: 60%.
2025 (pre-OBBBA): 40% scheduled.
2025 (post-OBBBA, after January 20, 2025): 100% restored permanently.
2026 and forward: 100% (permanent restoration).
The OBBBA restoration is significant for cost segregation planning. Under the phase-down framework, the value of a cost segregation study was declining year over year because the bonus depreciation rate was declining. With 100% bonus depreciation permanently in place, the cost segregation study's value is restored to its 2017-2022 peak.
For a typical commercial property with 30% of basis reallocated to 5/7/15-year property and 100% bonus depreciation applied, the first-year deduction effectively includes 30% of the building basis in year one rather than spread across decades. For a $5 million property, that means $1.5 million of immediate deduction rather than the gradual depreciation over 39 years.
What are look-back cost segregation studies and how does Form 3115 work?
A look-back cost segregation study identifies missed §1245 reallocations on properties already in service. The taxpayer files Form 3115 to change accounting methods and claims cumulative missed accelerated depreciation in a single year through a §481(a) adjustment, without amending prior returns. This is available for any property still in service.
Cost segregation studies are not limited to the year of acquisition. A "look-back" study can identify previously missed §1245 reallocations on a property that has been in service for several years, and catch up the missed accelerated depreciation through a Form 3115 (Application for Change in Accounting Method) filing.
The catch-up mechanism uses a §481(a) adjustment that allows the full cumulative accelerated depreciation to be claimed in a single year (the year of the change). For a property that has been depreciated under 39-year treatment for 5-7 years, a look-back study can identify substantial accumulated deductions that were missed and recover them in the year of the accounting method change.
The Form 3115 process requires:
Filing within the appropriate time window (generally with a timely-filed original return for the change year).
Identifying the specific accounting method change being made.
Including the §481(a) adjustment calculation.
Maintaining the supporting cost segregation study documentation.
The IRS generally provides automatic consent for the change from one depreciation methodology to another (the underlying §1245 vs §1250 classification doesn't require IRS approval; only the change in method does, and Rev. Proc. 2024-23 and similar guidance provide automatic consent procedures).
What is the depreciation recapture trade-off with cost segregation?
Accelerated depreciation from cost segregation triggers recapture on sale. Section 1245 property faces ordinary income recapture on accumulated depreciation. Section 1250 property and land improvements benefit from a lower maximum 25% unrecaptured gain rate. The trade-off favors cost segregation for properties held 10 or more years, where time value of money outweighs recapture.
The accelerated deduction from cost segregation comes with a corresponding recapture liability when the property is sold:
| Property Type | Recapture Rate on Sale | Notes |
|---|---|---|
| §1245 personal property | Ordinary income rates (up to 37%) | Recapture applies to the extent of accumulated depreciation; can be material for substantial §1245 reallocations |
| §1250 real property | Maximum 25% (§1250 unrecaptured gain) | Much more favorable than ordinary income rates |
| §1250(c) land improvements | Maximum 25% | Treated as §1250 property for recapture purposes |
The recapture trade-off matters most when a property is sold in the early years after acquisition. For a property held 3-5 years, the accelerated depreciation produces substantial current-year tax savings, but the recapture on sale claws back much of the benefit. For a property held 10+ years, the time value of money and the typically reduced recapture impact tilt the analysis strongly in favor of cost segregation.
The standard planning guidance: cost segregation is most valuable for properties held long-term or for properties where the investor wants to use accelerated depreciation to offset other current income, and is least valuable for short-hold strategies where the recapture quickly returns the deduction.
How does cost segregation interact with §1031 exchanges?
When a cost-segregated property is sold in a §1031 exchange, the §1245 personal property portion cannot be deferred because the TCJA limits §1031 to real property only. The §1245 gain must be recognized currently. A new cost segregation study can be performed on the replacement property for additional accelerated depreciation.
Cost segregation interacts with §1031 like-kind exchanges in two ways:
When selling a property in a §1031 exchange, the accelerated depreciation taken on the property carries into the replacement property as deferred gain. The §1245 portion of the deferred gain remains §1245 character and is subject to ordinary income recapture if the replacement property is later sold outside a §1031 exchange.
A cost segregation study can be performed on the replacement property in a §1031 exchange, providing accelerated depreciation on the new property even though the original property's basis has been carried over.
The §1031 framework's general rule that "real property is like-kind to real property" works at the §1250 building level; the §1245 components technically would not be like-kind to each other under pre-2017 rules, but the TCJA limited §1031 to real property only, so §1245 personal property is no longer eligible for §1031 deferral in any event. For cost segregation purposes, this means the §1245 portion of the gain on a real estate sale must be recognized currently; it cannot be deferred through §1031.
How does cost segregation coordinate with other small business provisions?
Cost segregation coordinates with §179 expensing (available for reallocated §1245 components), §263(a) capitalization rules, §168 MACRS recovery periods, §199A QBI calculations, and §1411 NIIT. The accelerated depreciation generated by a cost segregation study flows through each of these provisions, affecting deduction limits, QBI computation, and net investment income.
Cost segregation operates in coordination with several other provisions in the Halstonberg small business pillar:
§179 immediate expensing is available for qualified §1245 property (not §1250). After a cost segregation study identifies §1245 components, §179 can be elected on those amounts up to the annual §179 cap ($1.16 million for 2026, phased out for businesses with substantial §179 property purchases).
§263(a) tangible property capitalization determines what costs must be capitalized vs. deducted as repairs in the first place. The interaction with cost segregation is that components that are capitalized under §263(a) can then be classified through cost segregation; components deducted as repairs are not capitalized and don't enter the cost segregation analysis.
The MACRS half-year, mid-quarter, and mid-month conventions apply to the reallocated amounts.
§199A QBI deduction is reduced by the cost segregation depreciation deductions for purposes of the QBI calculation. The interaction can be substantial for real estate investors whose QBI calculation depends on the W-2 wages and unadjusted basis limitations.
Cost segregation's accelerated depreciation flows through to reduce NIIT exposure for high-income investors.
Practical guidance
The threshold for a cost segregation study is generally a property with at least $1 million in depreciable basis. Studies cost $5,000 to $25,000 depending on property size. With 100% bonus depreciation permanently restored by the OBBBA, the first-year deduction benefit is substantial, and engineering-based methodology is essential for audit defense.
For real estate investors considering cost segregation:
The threshold question is whether the financial benefit justifies the study cost. Cost segregation studies typically cost $5,000 to $25,000 depending on property size and complexity. For properties under $1 million depreciable basis, the study may not produce enough first-year deduction to justify the cost. For properties over $5 million, the study almost always pays for itself many times over.
The OBBBA bonus depreciation restoration is a substantial benefit. Properties placed in service after January 20, 2025 qualify for 100% bonus depreciation; cost segregation on those properties produces immediate deductions much larger than under the phase-down framework.
Engineering-based methodology is essential. The IRS specifically disfavors rule-of-thumb studies; using a qualified cost segregation specialist with engineering credentials is the foundation of audit defense.
Look-back studies are available for previously-acquired properties. The Form 3115 accounting method change procedure allows missed accelerated depreciation to be recovered in a single year through the §481(a) adjustment.
Plan the recapture exposure. For properties expected to be sold within 3-5 years, model the ordinary income recapture on §1245 reallocations to ensure the net benefit remains positive.
For properties involving §1031 exchanges, the §1245 portion of accumulated depreciation must be recognized on sale; build this expectation into exchange planning.
Document the study and retain it for the entire holding period. The IRS can audit the depreciation positions established in the cost segregation study at any point during the property's ownership; the study documentation is the audit defense.
Cost segregation is a mature, well-established planning technique. The IRS has a clear framework for evaluating studies, the case law is settled at the high level, and the financial benefits are substantial. The execution is where the value is created or lost; using qualified specialists who follow the ATG quality framework is the difference between a defensible accelerated depreciation position and an audit exposure.