Treas. Reg. §1.48-1

Where this comes from

In 1962 Congress created the investment tax credit, a credit for buying business equipment. Buildings did not qualify, so the line between equipment and building instantly became valuable. Treasury drew that line in Treas. Reg. 1.48-1, issued in 1964.

The credit itself was repealed for most property in 1986, but the definitions never died. Courts kept using them, and in 1997 the Tax Court's Hospital Corporation of America decision adopted them for sorting property under modern depreciation law. A sixty-year-old regulation became the foundation of cost segregation.

What it established

Subsection (c) defines tangible personal property as any tangible property except land and improvements to it, such as buildings, other inherently permanent structures, and their structural components. It says local law does not control, and that machinery and equipment can be personal property even though located outside a building or affixed to the ground.

Subsection (e)(2) defines structural components: parts that relate to the operation or maintenance of a building, including walls, floors, ceilings, permanent coverings, windows, doors, central air conditioning and heating, plumbing, electric wiring, and lighting fixtures.

The same subsection carves out the sole justification exception. Machinery qualifies as personal property, not a structural component, when the sole justification for installing it is that it is required to meet temperature or humidity needs essential to other machinery or to processing materials or product, even if it incidentally makes the space more comfortable for people.

How it shows up in a study

Every classification in a study runs through these definitions. Is the item part of the building's operation or maintenance, or does it serve the business conducted inside? Decorative lighting, dedicated equipment power, and removable finishes argue for personal property. Walls, windows, and the base building systems stay structural.

The sole justification test is the support behind process HVAC claims, like cooling that exists for server rooms, commercial kitchens, or production equipment. A study making that claim documents what the unit serves and why the building's people-comfort system could not do the job.

What it does not mean

This regulation does not say that attachment decides the answer. Things bolted down can be personal property, and the permanence question gets its own test from the Whiteco factors. It works the other way too: calling something equipment in a contract does not make it personal property if it functions as part of the building.

The sole justification exception is narrow. Comfort HVAC that also happens to cool some equipment does not qualify. The machinery must exist because the equipment or product requires it. Studies that stretch this exception are a known exam target.