What actually qualifies for cost segregation

The short answer

Cost segregation has no application form and no IRS approval step. There is nothing to apply for. The method is simply a more detailed way of depreciating real property that you already own: instead of writing the whole building off over 27.5 years (residential rental) or 39 years (commercial), an engineering-based study identifies the portions that the tax code allows to be depreciated faster — over 5, 7, or 15 years.

So the real question is never "am I allowed?" It is whether you own depreciable, income-producing real property with enough reclassifiable cost to make a study worthwhile. Almost any building you rent out or use in a business qualifies. The one that does not is the home you live in.

Property requirements

The property has to be something you depreciate — that is, real property held to produce income or used in a trade or business. The IRS describes this depreciable basis in Publication 946, and the engineering method for splitting it is laid out in the IRS Cost Segregation Audit Techniques Guide (Publication 5653). If a property fits those, it qualifies.

In practice that covers a wide range:

• Residential rental — single-family rentals, duplexes, and apartment buildings depreciated over 27.5 years.
• Commercial property — office, retail, industrial, medical, self-storage, and similar, depreciated over 39 years.
• Short-term rentals (STRs) — furnished Airbnb-style properties, which often carry an unusually high share of reclassifiable furnishings and fixtures.
• Mixed-use and renovated property — the depreciable improvements still qualify even where part of the parcel is land or owner-occupied.

What does not qualify is straightforward. A primary residence is not depreciated, so there is no depreciation to accelerate. Raw land with no building or improvements is not depreciable either — land is never written off, which is exactly why a study separates land value out before it does anything else. And any property you simply do not depreciate on your return falls outside the method. A house you live in but rent out a room or unit of (a "house hack") qualifies only for the rented, business-use portion.

Owner requirements

You qualify as the owner of the depreciable property, regardless of how you hold title. The same study works whether the building sits in your personal name, a single-member LLC, a partnership, or an S-corporation — the accelerated depreciation flows through to wherever that entity's income is reported. Leaseholders are a narrower case: a tenant who pays for build-out can study their own leasehold improvements, but not the landlord's building.

Ownership is necessary; it is not sufficient on its own to produce a tax benefit. Accelerated depreciation creates paper losses, and whether those losses offset your other income in a given year depends on the passive activity loss rules under §469, your entity structure, your filing status, and the income you have to absorb them. A high-bracket owner with rental or business income against which the losses can land tends to see the most immediate effect; a W-2-only owner usually needs a §469 path — real estate professional status or the short-term-rental exception — for the losses to be usable now rather than suspended. That is an outcome question, not a qualification question, and it is covered in our passive loss rules guide.

Timing requirements

The only timing concept that matters for eligibility is the placed-in-service date — the day the property was ready and available for its intended use, typically when you began renting it or put it to business use. Depreciation runs from that date, and the bonus depreciation rate that applies to the reclassified components is set by the placed-in-service year, not the year you order the study. Bonus has been stepping down (100% for property placed in service in earlier years, then 80%, 60%, and lower in later years), which is one reason the modeled first-year numbers differ property to property.

There is no minimum holding period. You do not have to have owned the property for any particular length of time, and you do not lose eligibility by having owned it for years. A property placed in service several years ago can still be studied through a lookback: a study run today computes the depreciation that could have been taken since the placed-in-service date, and the cumulative catch-up is claimed in the current year through a §481(a) adjustment on an accounting-method change — no amended returns required. Our guide on studying a property you have owned for years walks through this, and catchupdepreciation.com covers the catch-up mechanism in depth.

What a study actually reclassifies

A study does not change the building's total cost. It reads the structure and re-sorts the costs into the recovery periods the tax code already permits, moving non-structural components out of the long 27.5- or 39-year life and into 5-, 7-, or 15-year lives. The load-bearing shell, roof, and core systems stay long-lived; the items that come along for the ride do not.

Typical reclassified components include:

• Personal property (5- and 7-year) — flooring and carpet, cabinetry and millwork, appliances, window treatments, decorative lighting, and dedicated electrical or plumbing that serves specific equipment rather than the building as a whole.
• Land improvements (15-year) — site work outside the building footprint: paving and parking, sidewalks, fencing, site lighting, and landscaping.

The share that lands in these faster categories is an engineering estimate, not a fixed figure — it depends on the property's construction and use, which is why an STR full of furnishings reclassifies differently than a bare warehouse. The resulting first-year depreciation is a modeled tax estimate: it depends on the §481(a) catch-up, the bonus rate for the placed-in-service year, state conformity, §469, and your entity structure. Whether a study is worth running for a given property is a separate calculation, covered in is it worth it and by property type.

What makes a study hold up

The reason cost segregation is a defensible position and not a guess is methodology. The IRS Cost Segregation Audit Techniques Guide (Publication 5653) describes an engineering-based approach as the most reliable: components are identified from plans, cost records, and a site inspection, then valued and assigned to their proper recovery periods with documentation behind each figure. A study built that way carries its own support — a component-by-component breakdown, the basis for each classification, and the placed-in-service and basis facts the depreciation rests on.

That engineering record is what makes the reclassification reviewable, and it is the standard a Cost Seg Smart study is built to. If you want a study run on your property, you can order one here.

If you would rather sanity-check eligibility first, the fastest path is the qualifier on our homepage — six questions, an honest read on whether your property fits, and an estimated range in about thirty seconds.