A cost segregation study is an engineering-based tax analysis that reclassifies components of commercial real estate from 39-year depreciation to faster 5-, 7-, or 15-year schedules — dramatically accelerating deductions. Studies typically cost $5,000–$25,000 and generate first-year tax savings several times the study fee.
Under standard tax rules, commercial real estate depreciates over 39 years (residential rental over 27.5 years). A cost segregation study identifies building components that qualify for faster depreciation under MACRS (Modified Accelerated Cost Recovery System): personal property (5–7 year), land improvements (15 year), and remaining structure (39 year). Personal property components include: carpeting, specialty lighting, decorative features, removable partitions, countertops, wall coverings, and certain mechanical and electrical systems serving specific equipment rather than the building generally. Land improvements include parking lots, landscaping, sidewalks, fencing, and outdoor lighting. The building shell, load-bearing walls, roof, and core HVAC systems remain 39-year property. The reclassification dramatically accelerates deductions in early years. Combined with bonus depreciation (100% first-year expensing for qualified property through 2022, phasing down 20%/year thereafter — 40% for 2025 under current law), cost segregation can generate substantial first-year NOLs or deductions for real estate investors and business property owners. Study economics: A $2M commercial building typically has 20–40% of its cost reclassifiable to shorter-lived categories. On a $2M building with 30% reclassifiable ($600K), a 5-year property at 40% bonus depreciation generates $240K of first-year additional deductions. At a 37% tax rate, that's $88,800 of first-year tax savings — on a $10K–$15K study fee. ROI is typically 5–10x in Year 1. Cost segregation requires a qualified study performed by engineers and tax professionals. The IRS Cost Segregation Audit Techniques Guide (ATG) describes acceptable methodologies. Studies must be documented and defensible — poorly prepared studies are a common audit target.
Cost segregation is most valuable for: businesses that own (not lease) commercial real estate; properties with purchase or construction cost of $500K+; owners in high income tax brackets (32%+); owners who plan to hold the property at least 3–5 years; and businesses that purchased or built property in the last 15 years (look-back studies can capture missed depreciation without filing amended returns, using a 'catch-up' mechanism under IRS Rev. Proc. 2002-9). If you're leasing rather than owning your space, cost segregation doesn't apply.
A properly documented study done by qualified professionals does not meaningfully increase audit risk. The IRS publishes a Cost Segregation Audit Techniques Guide that defines acceptable study methodology. Studies that use the 'residual estimation method' (estimating reclassifiable components without an engineering analysis) are more vulnerable than engineering-based studies with component-level documentation. Quality of the study matters significantly.
Depreciation recapture. When you sell, depreciation claimed on personal property (5/7-year) is recaptured as ordinary income (Section 1245 recapture) — taxed at your ordinary rate, up to 37%. Depreciation on real property (15/39-year) is subject to unrecaptured Section 1250 gain — taxed at up to 25%. If you've claimed significant first-year bonus depreciation via cost seg, your recapture tax on sale can be substantial. 1031 exchanges can defer recapture.