For owners of high-end short-term rentals, luxury rental homes and upscale multifamily properties, interior investment can represent a meaningful share of total property cost. Custom millwork, decorative lighting, premium appliances, fitted cabinetry, carpeting and furnishings can add considerably to an upscale property’s cost. Tax treatment depends on how those costs are classified. A cost segregation study can identify qualifying components embedded in building costs and assign them shorter recovery periods.
What an engineering-based study identifies
A California cost segregation study reviews acquisition, construction and improvement costs, then classifies eligible assets according to their federal tax treatment and recovery period. For an upscale rental, that can include certain decorative lighting, millwork, carpeting, wall coverings and electrical components that qualify as shorter-life property when the facts support the classification.
The distinction matters because separately purchased furniture and FF&E are depreciated on their own schedules whether or not a study is performed. The value of a cost segregation study lies in identifying qualifying components that are already embedded in the building’s capitalized cost, then separating them from longer-lived structural property.
Where luxury interiors can matter
Consider a client who acquired a California apartment building in 2019 for $5,025,781, with land valued at $3,050,449. A full engineering-based cost segregation study produced an estimated $340,955 in first-year tax savings and a 90:1 payback ratio.
The example illustrates why the details of an upscale interior deserve careful review. An engineering-based study examines construction records, invoices, plans and the physical characteristics of the property to identify assets that can receive shorter recovery periods. Specialty millwork, decorative elements and certain electrical components can warrant closer attention.
Separately purchased furniture and FF&E remain a distinct category. Furniture used in a rental property generally has a five-year federal recovery period, while qualifying appliances such as refrigerators and stoves can also have five-year treatment. Those assets follow their own depreciation schedules regardless of whether a cost segregation study is commissioned.
Keep structural components separate
Premium finishes do not automatically become short-life property. Central HVAC, plumbing, roofing and windows are generally Section 1250 structural components that remain on the applicable 27.5- or 39-year schedule. Free-standing or portable equipment can receive different treatment when it qualifies as Section 1245 personal property, including portable AC units.
Short-term rental owners also need to keep two separate tax tests in view. Under IRC Section 168(e)(2), whether property receives the 27.5-year residential rental classification or the 39-year nonresidential classification depends on applicable transient-use rules, including the 30-day threshold. The seven-day average-stay rule belongs to the separate Section 469 passive-activity exception and does not determine the building’s depreciation period.
Passive-loss rules still matter
Accelerated deductions are not automatically usable against other income. Under IRC Section 469, losses from rental activity are generally passive, meaning they suspend and carry forward against future passive income, or release on disposition, rather than offsetting wages or business income in the year they arise. At the federal level, two exceptions apply. Real Estate Professional status under Section 469(c)(7) requires more than 750 hours annually in real property trades or businesses, more than half of total working time and material participation. Separately, the short-term rental exception under Reg. 1.469-1T(e)(3)(ii)(A) applies where average guest stay is seven days or less, and the owner materially participates. California is the important exception here: the state does not conform to Section 469(c)(7), so real estate professional status does not carry over to a California return even where it is established federally. Material participation requires satisfying one of the seven tests in the regulations – most commonly the 500-hour test, or the test requiring more than 100 hours with no other individual participating more.
For California owners, that state treatment can make the federal and state calculations look quite different. A federal deduction created through accelerated depreciation does not automatically produce the same California tax result, so both sets of rules need to be considered when evaluating the benefit of a study.
Federal bonus depreciation, California adjustment
The One Big Beautiful Bill Act, P.L. 119-21, made 100% bonus depreciation permanent for qualifying property acquired and placed in service on or after 20 January 2025, reversing the phase-down that had been stepping the rate down through 80%, 60%, 40%, 20% and finally 0%.
The federal rule can increase the first-year deduction available for qualifying shorter-life property. California does not conform to federal bonus depreciation, so the first-year deduction is federal only. A California return requires an add-back and a separate state depreciation calculation.
Look-back studies and the eventual sale
A property does not necessarily have to be newly acquired for an owner to consider cost segregation. When a qualifying change in depreciation method is available for property placed in service in an earlier year, the change is generally handled through Form 3115 as an accounting-method change, with the applicable catch-up adjustment taken in the current year. It is not handled through an amended return.
Accelerated depreciation is a timing benefit, not a permanent one, and the reckoning comes at sale. The 5- and 7-year personal property a study reclassifies is Section 1245 property, recaptured at ordinary income rates up to 37%. The 15-year land improvements and the building itself are Section 1250 property, where depreciation claimed in excess of straight-line is ordinary income, and the straight-line portion becomes unrecaptured Section 1250 gain, capped at 25%. Recapture can be deferred through a Section 1031 exchange. This is why the hold period matters: a study generally makes sense on a three-to-five-year minimum hold and is most compelling at five years or longer.