Cost Segregation: Depreciation You Are Entitled To Now, Not Over 39 Years

The default is slow, and the default is optional

When you buy, build, or substantially renovate a building, the standard treatment is to depreciate the whole thing over 27.5 years for residential rental property or 39 years for commercial. That is the path of least resistance, and it is what most returns do by default.

But a building is not one asset. It is a structure plus a large collection of components that have their own, much shorter, recovery periods under the tax rules. A cost segregation study is the engineering exercise of identifying and valuing those components so they can be depreciated on the schedule the law actually assigns them rather than being swept into the 39-year bucket.

What actually gets reclassified

Typical five- and seven-year property includes things like dedicated electrical serving specific equipment, decorative lighting, cabinetry and millwork, floor coverings such as carpet and vinyl, and specialty plumbing. Fifteen-year land improvements cover site work outside the building footprint — parking lots, curbing, sidewalks, landscaping, site lighting, and drainage.

The study is not an accounting estimate. A defensible one is engineering-based: it works from construction documents, invoices, and a site inspection to allocate cost on an itemized basis. That distinction matters if the allocation is ever examined, which is the same reason the documentation discussion below is not optional.

Why 2025 changed the arithmetic

The One Big Beautiful Bill Act restored 100% bonus depreciation on a permanent basis for qualifying property acquired after January 19, 2025, after several years of it phasing down. Short-life property identified by a study is generally bonus-eligible.

The practical effect is that reclassified basis is no longer merely accelerated over five or fifteen years — a substantial portion of it may be deductible in the year the property is placed in service. That makes a study meaningfully more valuable than it was during the phase-down years, and it is worth revisiting the math if you priced one out in 2023 or 2024 and passed.

You may not have missed the window

A common assumption is that a study only makes sense in the year you acquire the property. That is not the case. If you have owned the building for several years and never had a study done, a Form 3115 change in accounting method can capture the depreciation you should have taken, as a catch-up adjustment, without amending old returns.

Whether that is worth doing depends on your basis, your holding period, and what your income looks like in the catch-up year. Sometimes the answer is that it is not worth the fee, and we will say so.

Who this genuinely fits, and who it does not

It tends to fit owners of commercial buildings, residential rental portfolios, and owner-occupied business property, particularly after a purchase or a significant renovation. Larger basis and longer expected hold generally mean a better return on the study fee.

It fits less well where basis is small, where the property is about to be sold, or where accelerated deductions cannot actually be used because of passive activity limits or a lack of offsetting income. Depreciation timing also interacts with recapture on sale. Any of these can flip the answer, which is why the study is preceded by a review rather than a sales pitch.

What the process actually involves

A study starts with documents rather than a site visit: the closing statement or construction contract, the depreciation schedule, architectural drawings if they exist, and invoices or cost breakdowns. From those, the engineering analysis allocates the total cost across asset classes, item by item, with each allocation traceable back to a source document.

A site inspection follows for most properties, to verify what is actually there and to photograph components that the drawings do not capture. The deliverable is a written report that documents the methodology and supports every reclassification, because the report is what has to stand up if the allocation is ever examined. A spreadsheet of percentages with no engineering behind it is not the same product, and it is worth asking any provider which one you are buying.

Recapture, and the question people forget to ask

Accelerating depreciation changes when you take deductions, not whether you ultimately take them. When the property is sold, some of the accelerated depreciation is recaptured, and personal property recapture is taxed differently from the unrecaptured section 1250 gain that applies to the building itself.

For an owner planning to hold long term, the time value of deducting now generally outweighs the recapture consequence later. For an owner who expects to sell within a few years, that calculus can invert. This is exactly the sort of thing that should be modeled before you commission a study rather than discovered at closing, and it is a question a firm selling studies on volume has little incentive to raise.

Talk to an Enrolled Agent

This article is general information, not individual tax advice. Whether a study benefits you depends on your basis, holding plan, and ability to use the deductions it accelerates — nothing here predicts a result for your property. Our $350 Tax Opportunity Scan covers the initial look and is credited toward the study if you proceed. To talk it through, book your free review, or call or text (323) 900-0305.