What the Special Depreciation Allowance Actually Is
Commercial property owners often hear “bonus depreciation” and “special depreciation allowance” used as if they’re two different things. They’re not. Both terms describe the same provision under Internal Revenue Code Section 168(k): a rule that allows the cost of certain qualifying property to be deducted in the year it’s placed in service, rather than spread out over its full depreciation schedule. For owners focused on cash flow, understanding exactly what qualifies is the difference between a modest deduction and a substantial one.
Why the Building Itself Doesn’t Qualify, But Parts of It Do
The first thing worth clearing up is that the building itself doesn’t qualify. Commercial real estate is generally depreciated over 39 years (27.5 years for residential rental property), and the special depreciation allowance is limited to property with a recovery period of 20 years or less. That’s precisely why cost segregation exists as a strategy. A qualified engineering based study looks past the building’s overall structure and identifies individual components inside it that carry much shorter recovery periods: specialty electrical and plumbing tied to equipment, certain site improvements, carpeting and other non structural interior finishes, and similar assets typically classified as 5, 7, or 15 year property. Those components are exactly the category of property the special depreciation allowance was designed to reach.
The Original Use Rule, and the Used Property Exception
Beyond the recovery period requirement, the property generally needs to meet an “original use” standard, meaning the taxpayer claiming the deduction is the first one to put it to use. There’s a notable exception for used property, added under the Tax Cuts and Jobs Act, that has become especially relevant for buildings that change hands. If a property is acquired by purchase rather than through a related party transaction, an inheritance, or a like kind exchange, and the taxpayer or a predecessor didn’t previously have a depreciable interest in it, that used property can still qualify. This matters directly for cost segregation on acquired buildings, since it opens the door for newly purchased assets, not just newly constructed ones, to capture the benefit.
Qualified Improvement Property
Qualified improvement property is another category worth knowing by name. It covers improvements made to the interior of nonresidential real property after the building was originally placed in service, excluding work tied to enlarging the building, elevators, escalators, or the internal structural framework. Since a 2020 technical correction fixed an earlier drafting error, qualified improvement property carries a 15 year recovery period and is fully eligible for the special depreciation allowance, which has made tenant buildouts and interior renovations a meaningful opportunity for owners who might not otherwise think to look there.
How the Allowable Rate Has Changed, and Why It Matters Now
The rate at which qualifying property can be deducted has shifted considerably in recent years, and that history still matters. Under the Tax Cuts and Jobs Act, the allowance was set at 100% for property placed in service from late 2017 through 2022, then began stepping down: 80% in 2023, 60% in 2024, and 40% for property placed in service in the first weeks of 2025. The One Big Beautiful Bill Act reversed that phase down, restoring the allowance to 100% for qualifying property acquired and placed in service after January 19, 2025, with the intent that the rate hold at that level going forward rather than resume declining. For owners weighing the timing of a purchase, a renovation, or a new build, that reinstated 100% rate is a significant reason a cost segregation study is worth revisiting now, even for projects that were shelved when the lower rates applied.
Why the Classification Still Has to Hold Up
None of this changes the core discipline required to claim the deduction correctly. Every asset identified still has to independently meet the recovery period, original use or used property, and placed in service requirements on its own facts, which is exactly why an engineering based approach to classification, rather than a generic estimate, holds up under IRS scrutiny. CSSI has spent more than 23 years and over 65,000 completed studies building that discipline into every cost segregation engagement, so property owners can claim the full benefit they’re entitled to without taking on unnecessary audit risk.
Frequently Asked Questions
Does a commercial building qualify for the special depreciation allowance?
No, the building structure itself doesn’t qualify because its standard recovery period exceeds 20 years. The allowance applies to shorter lived components inside the building, which is what a cost segregation study is designed to identify.
Can used property qualify for bonus depreciation, or only new construction?
Used property can qualify, provided it was acquired by purchase rather than from a related party or through an inheritance or like kind exchange, and neither the taxpayer nor a predecessor previously had a depreciable interest in it.
What is qualified improvement property, and does it qualify?
It’s an improvement to the interior of a nonresidential building made after the building was originally placed in service, excluding items like building enlargements, elevators, escalators, or internal structural framework. It carries a 15 year recovery period and is fully eligible for the special depreciation allowance.
What percentage can currently be deducted under the special depreciation allowance?
Qualifying property acquired and placed in service after January 19, 2025 is eligible for a 100% allowance under the One Big Beautiful Bill Act. Property placed in service earlier is generally locked into the rate that applied in that year, such as 80% in 2023 or 60% in 2024.
How does cost segregation relate to the special depreciation allowance?
Cost segregation is the engineering process that identifies which components of a building qualify for a shorter recovery period in the first place. Without that classification, most owners would depreciate the entire building over 39 years and miss the components eligible for the allowance entirely.
How can I find out what qualifies in my property?
The specific mix of qualifying assets depends on the building’s construction, use, and history. Request a free analysiswith a CSSI specialist to see what your property’s asset mix could mean for this year’s deductions.
