ParcelProof How it worksToolsBlogGuidesFAQ

Blog · Basics · 2026-08-05 · 2 min read

Your property class code, and why it decides who you get compared to

The class determines the pool of comparable properties. A wrong class quietly ruins every comparison.

Every parcel carries a class code describing its use — improved residential, vacant residential, farmland, commercial, industrial, exempt. It is administrative, and it decides more than it looks like it does.

It selects your comparables

Uniformity arguments compare you to properties of the same class. If your house is coded as something else, you are being compared with the wrong pool and the comparison is meaningless in both directions.

Where it goes wrong

Newly built homes sometimes stay coded as vacant land for a cycle. A parcel that once had a shop can stay commercial after conversion. A property split or combined can inherit the wrong code. Land in a subdivision that has been built on can remain farmland until someone notices.

Why it can cut both ways

A wrong class is not automatically bad for you — farmland assessment is far lower than residential, and an incorrectly farm-coded lot is a benefit until it is corrected. Know which situation you are in before drawing attention to it.

Check it

Your class is on the notice and on the county parcel page. Compare it to a neighbour whose property is genuinely like yours. If they differ and the properties do not, ask the assessor why — that is a factual question with a factual answer, and it does not require an appeal to raise.

This is general information about how Illinois assessments and appeals work. It is not legal advice, not an appraisal, and not a prediction about your case. Deadlines and rules differ by county — check yours with your Board of Review.

Check your own assessment free →

More on Basics

What an assessed value actually is It is not a fact the county issued. It is an opinion produced by a model, and opinions can be wrong.Assessed value, market value, fair cash value: three different numbers They are related by a ratio set in statute, and confusing them is the most common reason an appeal goes nowhere.The 33⅓% rule, and the counties it does not apply to Illinois assesses at one third of fair cash value — except in Cook County, and except for farmland.The equalization factor, and why your assessment changed without anyone visiting The state multiplier adjusts a whole county at once. It is not a reassessment, and it is not appealable.

← Uniformity: the argument that does not need an appraisal · How to read your assessment notice →