Cost Segregation — IRS Pub. 5653 Audit Techniques Guide

Plain-English definition

A cost segregation study is an engineering analysis that identifies and reclassifies portions of a building’s depreciable basis from the 27.5-year (residential rental) or 39-year (nonresidential) MACRS structural class into the shorter accelerated classes — 5-year personal property (§1245), 7-year specialty property, and 15-year land improvements (§1250).

The reclassified components then qualify for §168(k) bonus depreciation — currently 100% for property placed in service after January 19, 2025 — and shorter-life MACRS depreciation under §168. The arithmetic compresses years of would-be depreciation into the first year.

The authoritative IRS guidance

Pub. 5653 — the Cost Segregation Audit Techniques Guide (ATG) — is published by the IRS as operational guidance for examiners. Its purpose is to define what examiners look for when reviewing a study, which makes it the authoritative reference for taxpayers performing studies.

The ATG has eight chapters:

1. Introduction and overview
2. Legal framework (statute, regulations, key cases)
3. Cost segregation methodologies
4. Quality cost segregation study elements
5. Reviewing a cost segregation study
6. Specific industry guidance (retail, hotels, restaurants, etc.)
7. Specific industry guidance, continued
8. Index

Chapters 6 and 7 — specific industry guidance — are unusual in IRS publications: industry-by-industry examiner instruction. Restaurants, retail, hotels, manufacturing, golf courses, and several other industries get their own examiner-focused write-up.

The legal framework

Cost segregation operates within IRC §168 (MACRS) and Rev. Proc. 87-56 (asset class table). It is not a separate statutory regime — it’s the application of existing MACRS classification rules to building components that would otherwise be lumped into the 27.5- or 39-year structural class.

The legal authority chain:

1. §168(a) requires depreciation under the applicable method, recovery period, and convention.
2. §168(e) classifies property by recovery period — 5-yr, 7-yr, 15-yr, 20-yr, 25-yr, 27.5-yr, 39-yr.
3. Rev. Proc. 87-56 lists ~150 asset classes by class life, which feed into the recovery period under §168(e).
4. Treas. Reg. §1.48-1(c) defines the “permanence test” — whether an item is part of the building or is “personal property” — by reference to whether removal would damage the structure.
5. Hospital Corporation of America v. Commissioner, 109 T.C. 21 (1997) — the seminal case applying these rules to identify components of a building that qualify as personal property.

The HCA case held that a hospital’s specialty MEP, decorative finishes, and other tenant-specific components properly classified as personal property (§1245) under the permanence test, despite being installed in a building. The IRS lost at the Tax Court, and the principles of HCA became the foundation of modern cost segregation.

What gets reclassified

The component schedule in a study identifies items that pass the §1.48-1(c) permanence test plus items that qualify as land improvements under Rev. Proc. 87-56 Class 00.3.

5-year personal property (Section 1245):

• Tenant-finish carpet, vinyl plank, and other resilient flooring
• Decorative interior partitions (movable, demountable, or tenant-specific)
• Specialty MEP — dedicated HVAC zones, specialty plumbing for kitchen or medical operations, specialty electrical for diagnostic equipment
• Decorative lighting (sconces, pendants, accent, cove)
• Wall coverings, decorative tile, specialty finishes
• Window treatments
• Cabinetry and millwork specific to tenant fit-out
• Audio/visual systems, security infrastructure
• Specialty industry equipment built into the building (kitchen equipment, exam-room casework, medical gas piping)

7-year specialty property (Section 1245):

• Built-in casework, reception desks, custom millwork (limited categories; most fit-out is 5-year)
• Specific specialty fixtures in specific industries

15-year land improvements (Section 1250 — but §1245 for recapture under §1245(a)(3)(D)):

• Parking lots (asphalt, subbase, striping, curbs, drainage)
• Sidewalks, curb cuts, ADA approaches
• Site lighting (parking lot poles, fixtures)
• Monument signage, pylon signage, building-mounted signage (when not structurally integral)
• Landscaping (plants, shrubs, sod, mulch, irrigation)
• Fencing, gates, perimeter security
• Storm drainage, retention basins
• Outdoor amenities (pool decks, BBQ pavilions, dog parks)

39-year structural (Section 1250) or 27.5-year residential rental:

• Building shell, structural framing, roof, foundation
• Base building HVAC (central plants, building-wide air handling)
• Structural plumbing and electrical service
• Permanent partitions structural to the building
• Elevators (always 39-year structural)
• Permanent fire suppression infrastructure
• Building permanent ceiling, structural ceiling grid

Reclassification percentages by property type

Published benchmarks across engineered studies (n=412 across nine commercial property classes; source: 2026 Commercial Cost Segregation Benchmarks dataset):

The variance between property types reflects the underlying physical composition — tenant-fit density relative to structural shell, site-improvement intensity relative to building basis, and era-of-construction component density.

The §168(k) bonus stack

Cost segregation’s economic significance comes from layering on §168(k) bonus depreciation. The 20-year-or-less recovery-period requirement for bonus eligibility excludes the 27.5- and 39-year structural classes — but the 5-yr, 7-yr, and 15-yr components identified through cost segregation are all under 20 years.

Worked arithmetic on a $5M commercial property placed in service in 2025 (100% bonus):

• Total depreciable basis (after 15% land): $4,250,000
• Cost segregation reclassification: 30% accelerated = $1,275,000
• Of which: 5-yr at $935,000, 7-yr at $55,000, 15-yr at $285,000
• Year-1 §168(k) bonus depreciation: $1,275,000 × 100% = $1,275,000
• Year-1 MACRS on 39-yr structural ($2,975,000 / 39, mid-month): ~$76,000
• Total year-1 deduction: ~$1,351,000
• Federal tax savings at 37% bracket: ~$500,000

Without cost segregation, the year-1 deduction would have been ~$109,000 — the entire $4.25M basis depreciated straight-line over 39 years.

The Form 3115 path for prior-year properties

A cost segregation study on a property acquired in a prior year captures the missed accelerated depreciation through Form 3115 under Rev. Proc. 2015-13. The §481(a) adjustment includes:

• Catch-up MACRS depreciation on the reclassified components for prior years
• Catch-up §168(k) bonus at the rate that applied in each placed-in-service year (100% in 2018–2022, 80% in 2023, 60% in 2024, 100% in 2025+)

The §481(a) adjustment is reported on the year-of-change return — no amended returns. Designated Change Number (DCN) 7 is the automatic-consent code for depreciation method changes associated with cost segregation.

Recapture on disposition

Components reclassified as §1245 property (5-yr, 7-yr, and 15-yr land improvements via §1245(a)(3)(D)) are subject to ordinary-income recapture under §1245 on disposition. The 100% bonus depreciation taken in year 1 is recaptured at up to 37% ordinary rates at sale.

The 27.5-yr or 39-yr structural portion remains §1250 property, with the bulk taxed as unrecaptured §1250 gain at the 25% maximum rate.

The net present value of a cost segregation study depends on:

1. Year-1 tax savings (deferral benefit)
2. Recapture at disposition (timing reversal)
3. Bracket spread between deduction year and disposition year
4. Hold period (time value of the deferred tax)
5. Whether §1031 exchange will defer recapture further

For long holds at stable brackets, NPV is materially positive. For very short holds (< 24 months) or rising-bracket assumptions, NPV can turn negative.

Common errors

1. Templating without engineering. Industry-standard percentages applied without site visit or component identification produces classifications that fail the Pub. 5653 quality test. The IRS ATG explicitly distinguishes engineered studies from “modeling” studies.

2. Missing the §163(j) ADS election interaction. A taxpayer that elected out of the business-interest limitation under §163(j)(7) is required to use ADS for certain real property — and ADS-classified property is not eligible for §168(k) bonus depreciation. The election forecloses the bulk of cost-seg benefit.

3. Filing amended returns instead of Form 3115. Cost segregation on a property held more than one year is a method change. Amending prior returns is the wrong procedural mechanism and can be disallowed by the IRS as failure to follow the §481(a) process.

4. Skipping the recapture analysis. The NPV of cost segregation depends on hold period and bracket-at-sale. A study performed without modeling the disposition can produce a net negative outcome if assumptions are wrong.

5. Treating 15-year land improvements as §1250. Land improvements are 15-year MACRS class but are §1245 property by reference under §1245(a)(3)(D). On disposition, they get full ordinary recapture, not §1250 treatment.

Sources

• Statute: 26 U.S.C. § 168 (MACRS); 26 U.S.C. § 1245 (recapture); 26 U.S.C. § 481(a) (method changes)
• Regulations: Treas. Reg. § 1.48-1(c) (permanence test); Treas. Reg. § 1.168(k)-2 (bonus)
• Revenue procedures: Rev. Proc. 87-56 (asset class table); Rev. Proc. 2015-13 (Form 3115 procedures)
• IRS publications: Pub. 5653 — Cost Segregation Audit Techniques Guide; Pub. 946 — How to Depreciate Property; Pub. 535 — Business Expenses
• Cases: Hospital Corporation of America v. Commissioner, 109 T.C. 21 (1997); Whiteco Industries v. Commissioner, 65 T.C. 664 (1975) (six-factor permanence test)
• Chief Counsel Advice: CCA 202612008 (QIP eligibility for owner-occupied portions)

Need an engineered cost segregation study for a specific property? The arithmetic depends on the property’s MACRS class, the placed-in-service date, the reclassification percentage achievable for the property type, and the §168(k) bonus rate at the time of placement. A property-specific engineered analysis produces the reclass schedule, the §168(k) computation, and the Form 3115 §481(a) calculation in a single deliverable.