Why Cost Segregation Works

By Jason Watson, CPA
Posted Sunday, July 12, 2026

How does all this black magic work? Before we get into the how does cost segregation work, and start tossing sticks, bricks, cabinets, sidewalks and hot tubs into different depreciation piles, we need to answer the bigger question: why are we allowed to do this at all? It feels naughty, right?

The short answer is that tax law does not always treat a building as one giant asset. Yes, the building itself is usually depreciated over 27.5 years for residential rental property or 39.0 years for nonresidential property. But not everything inside, attached to, or surrounding the building is necessarily the building.

Sidebar: A short-term rental property that has an average guest stay of 7 days or fewer where you materially participate in the activity is considered a nonresidential activity, and as such will be 39.0 years. We discuss the short-term rental (STR) loophole in great detail on page 247.

That is the whole cost segregation opportunity. As we mentioned previously, a depreciable building is generally IRC Section 1250 property. IRC Section 1245 property is different. This is generally tangible personal property and certain other shorter-life property.

In the cost segregation world, this might include appliances, certain flooring, decorative lighting, furniture, specialty electrical, some cabinetry, and other items that are not really part of the building’s bones.

1250 Versus 1245, Why Do You Care?

Not to get too far off track, but one of the big benefits of identifying property as IRC Section 1245 property is that it often becomes eligible for shorter depreciation periods, bonus depreciation, or Section 179 expensing where available. There are also separate rules for things like Qualified Improvement Property, or QIP for short, but we’ll save that fun for later.

There is a downside too. Depreciation recapture, which we have not fully discussed yet, treats IRC Section 1250 property more gently than IRC Section 1245 property in many situations. Unrecaptured Section 1250 gain is generally taxed at a maximum 25% rate, while Section 1245 depreciation recapture can be taxed at ordinary income tax rates. As such, this becomes a real tax planning consideration. Also, IRC Section 1245 property does not always escape depreciation recapture in a Section 1031 Like-Kind Exchange either. We expand on this and the wonderful 15% exception on page 478.

The classification depends on the facts. How is the item attached? Is it designed to remain in place permanently? Does it relate to the operation and maintenance of the building itself? Is it decorative, removable, dedicated to a specific function, or more like general building infrastructure? These questions matter because the answer determines whether the item is shorter-life property or stuck inside the long-life building bucket.

IRS Walks Through The Cost Segregation Door

Back to Hospital Corporation of America v. Commissioner, 109 Tax Court 21 (1997). The court recognized that just because something is inside a building, attached to a building, or hanging out near a building does not automatically mean it is the building.

Being less than thrilled with the court, the IRS responded with Action on Decision 1999-008, where it agreed only in pa. In tax-speak, that basically means, “Fine, we accept enough of this to move forward, but please do not mistake our acceptance for a) happiness or b) being wrong.” Specifically, the AOD from August 30, 1999, reads in part-

On their tax returns for 1985 through 1988, the taxpayers classified as tangible personal property certain items in hospital facilities constructed in those years and took depreciation deductions for them using a 5-year recovery period … The Commissioner determined that the items were structural components of the hospital facilities and not tangible personal property and, therefore, should be depreciated over the same recovery period as the facilities to which they related.

In the Tax Court, the taxpayers argued that the items constituted section 1245 property, and, therefore, were appropriately depreciated using a 5-year recovery period … Further, the Commissioner argued that section 168(f)(1) effectively operates to change the definition of tangible personal property after 1981, thereby precluding such property item from being classified as section 1245 property, if it is attached to a building and has utility beyond its relation to a particular piece of property. It was the Commissioner’s position that the items were structural components and thus section 1250 property and, therefore, should be depreciated over the same recovery period as the building to which they relate.

The Tax Court found that most of the assets at issue were section 1245 property. The Court rejected the Commissioner’s primary argument stating that the test developed with respect to ITC and Treas. Reg. § 1.48-1(e) were inappropriate after the enactment of ACRS in 1981. The court concluded, after reviewing the statutory and regulatory language and case law, that, while Congress did prohibit the use of component depreciation, there was no intent to redefine section 1250 property under ACRS to include property that had been section 1245 property for purposes of the investment tax credit.

As a result, the IRS relented, and stated in their AOD,

We acquiesce in this decision to the extent that the Tax Court held that the term “tangible personal property,” as defined under a pre-1981 ITC analysis, has continued viability under ACRS and MACRS. The issue as to whether the various disputed items are structural components or tangible personal property is a factual question. We do not agree with the court’s determination with respect to the various disputed properties. We cannot state, however, that the court was clearly erroneous.

The important takeaway from the Action on Decision is that the older tangible personal property analysis still has relevance under ACRS and MACRS. In English, the door stayed open for cost segregation. The IRS might argue about the classification of specific assets, but the overall framework survived.

This is why cost segregation studies lean so heavily on old investment tax credit concepts. Yes, old tax law is being used to interpret current tax law. Yawn.

Primary Test Of A Building Component

The IRS Cost Segregation Audit Techniques Guide explains that the primary test is whether the asset is a building or structural component of a building. If it is not a building or structural component, it might be IRC Section 1245 property. The guide also focuses on how permanently the asset is attached and whether it relates to the operation or maintenance of the building.

That last phrase is a big deal.

If an item is necessary and ordinary for the operation and maintenance of the building, it usually smells like a structural component. If an item is decorative, removable, dedicated to a specific use, or not part of the general building operation, it might smell like shorter-life property.

Neat. Here is the practical lens-

• 5-year or 7-year property is usually IRC Section 1245 property. This is where you often see appliances, furniture, certain flooring, decorative items, specialty wiring and similar assets.
• 15-year property is often land improvements, such as fencing, landscaping, parking areas, patios, sidewalks, exterior lighting and similar items. These are not depreciated over 27.5 or 39.0 years simply because they live outside the building and wave at it.
• 27.5-year or 39.0-year property is generally the building and its structural components. This is IRC Section 1250 property, and it is where the slower depreciation lives.

Can 15-year property involve both IRC Section 1245 and IRC Section 1250 questions? Yes. Do we need to turn this discussion into a lesson on land improvement property that directly supports manufacturing machinery? Um skip the following sidebar if you’re not feeling it.

Sidebar: Asset Class 00.3, as defined by the IRS, refers to Land Improvements and mentions that they can be either Section 1245 or Section 1250 property. This is because assets that are integral to the manufacturing / production process are defined as Section 1245 property in IRC Section 1245(a)(3)(B). Therefore, a plant could have inherently permanent improvements to the land that would be considered Section 1245 property because they support the manufacturing / production process. A massive diversion in a book about rental properties, but you’re better for it.

How does the IRS distinguish between Section 1245 and Section 1250 property? According to IRS Publication 5653 Cost Segregation Audit Technique Guide (ATG)–

From a regulatory standpoint, the primary test for determining whether an asset is § 1245 property eligible for ITC [investment tax credit] is to ascertain that it is not a building or other inherently permanent structure, including items which are structural components of such buildings or structures. In other words, if an asset is not a building or a structural component of a building, then it can be deemed to be § 1245 property. The determination of structural component hinges on what constitutes an inherently permanent structure, how permanently the asset is attached to such a structure and whether it relates to the operation or maintenance of the structure. See Treas. Reg. §§ 1.48-1(c)-(e).

ITC references investment tax credit. How does that matter? IRC Section 1245(a)(3) and Treasury Regulations Section 1.1245-3(b)(1) read that the distinction between tangible personal property (Section 1245) and structural components (Section 1250) should be based on the criteria once used to determine whether property qualified for the now repealed investment tax credit (ITC) under IRC Section 38.

Huh? The IRS is using old tax code to define current tax code. You still awake? In 1975, the IRS refined its definition and stated in Revenue Ruling 75-178,

Rather, the problem of classification of property as ‘personal’ or ‘inherently permanent’ should be made on the basis of the manner of attachment to the land or the structure and how permanently the property is designed to remain in place.

As such, the inherently permanent test, is illustrated in the landmark Whiteco Industries, Inc. v. Commissioner, 65 Tax Court 664 (1975) court case. That test looks at things like how the property is attached, whether it is designed to stay in place indefinitely, and whether it can be removed without destroying the asset or the building. No, we don’t bore you with all the factors, but it is an interesting read if you cannot get enough.

This is also why a cost segregation study needs support. A defensible cost segregation study should explain what was classified, why it was classified that way, what methodology was used, who prepared the analysis, what data was reviewed, and how the asset values reconcile back to the purchase price or actual project costs.

Courts opened the door. The IRS grumbled but accepted the framework. The ATG gives agents a roadmap for reviewing the work. And taxpayers get to separate rental property components into proper asset classes when the facts and documentation support it.

Next, let’s talk about the mechanics: the sticks, bricks, stuff inside, and all the wonderful little piles that make cost segregation useful.