Where to find recent sales data free
County recorder, assessor sales files, and IDOR declarations — no subscription needed.
Sales evidence is public. You do not need a paid data service.
The county recorder
Records every deed. Many Illinois recorders offer a free search by address or PIN showing date and often the transfer amount from the stamp.
The assessor's sales file
Assessors maintain sales used for their own analysis, and many publish recent sales by neighbourhood. This is the same data the assessment was calibrated on, which makes it hard to argue with.
Transfer declarations
Illinois requires a real estate transfer declaration (PTAX-203) on most sales, recording price and whether the sale was arm's length. Where available it is excellent evidence because it states the circumstances, not just the number.
What to record for each sale
PIN, address, sale date, sale price, and the characteristics that make it comparable. A sale you cannot tie to a PIN is a sale the board cannot verify.
Filter honestly
Exclude foreclosures, family transfers, estate sales under time pressure and portfolio deals — unless distress is your actual argument. Including them is the fastest way to have your whole set questioned.