What makes a comparable good enough to use
Similarity on recorded attributes, proximity, and nothing clever. Four tight ones beat twenty loose.
A board is deciding whether your comparables are like your property. Everything else follows.
The tests
- Same class. A comparable in a different class is not a comparable.
- Close in size. Both lot and building, within roughly 10%. A 2,000 sq ft house is not comparable to a 3,200 sq ft house however similar the street.
- Close in age. Construction era drives cost and condition assumptions.
- Nearby. Same neighbourhood code if the county publishes one, same town otherwise.
- Same style where it matters. A ranch and a two-storey of identical square footage can be assessed differently for defensible reasons.
How many
Three to five. A long list is not more persuasive — it gives the assessor a weak one to attack and invites the board to treat your whole set as loose.
The self-test
For each comparable, ask: if the assessor says "that property is not like yours", what is my one-sentence answer? If the answer is a recorded attribute — "same class, same town, lot within 4%, building within 6%, built two years apart" — keep it. If the answer is "it's round the corner", drop it.
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.