Step 2 Unit Of Property Analysis

By Jason Watson, CPA
Posted Monday, March 30, 2026

If your expenditure was too big to slide into the de minimis or small taxpayer safe harbors from Step 1, welcome to the jungle- we’ve got fun and games, as Axl would say.

Before you can apply any math or functional tests to figure out if you repaired or improved something, you must define the playground. What exactly are you fixing? In tax terms, this is called determining your Unit of Property (UoP).

Historically, the UoP was generally considered the entire building, including all its structural components. However, under the final Tangible Property Regulations, specifically 1.263(a)-3(e), the IRS explicitly requires you to carve out the building’s major internal systems from the building and its structural components.

This is actually a good thing.

The improvement versus repair analysis must be applied independently to the building structure and each of the following 8 key building systems:

• plumbing system
• electrical system
• HVAC system
• elevator system
• escalator system
• fire protection and alarm system
• gas distribution system, and
• the security system.

So, you have 9 total Units of Property if you count the building structure itself.

Why Does This Matter? Defining the UoP is arguably the most critical step in defending a repair deduction. Why? Because the UoP becomes the denominator for every test that follows.

You do not measure the scope of a plumbing repair against the value of the whole building. You measure the scope of a plumbing repair against the total plumbing system. Replacing 20% of a building sounds small. Replacing 20% of a plumbing system starts to feel very different.

If you skip this step and use the wrong denominator, you will either incorrectly capitalize a valid repair, or you will take an aggressive deduction that perhaps some suits at the IRS would disagree with.

Sidebar: Ironically, the same real estate investor who will happily pay thousands of dollars for a cost segregation study to aggressively carve up a property into discrete components for accelerated depreciation often completely abandon that disciplined, system-level thinking when analyzing a $15,000 plumbing invoice. The UoP rules require the exact same level of granular, system-level thinking in both contexts.

We mentioned the word denominator, and that suggests a mathematical equation or formula. The problem is how you measure that denominator—by dollars? by physical scope? We dig into these head scratchers in a bit.