Your property number can be found on your property tax bill or tax assessment notice. You must write the number exactly as it appears on the bill or notice. It's sometimes called a property index number, parcel number, or permanent index number. It's often a 10-digit or 14-digit number and will be formatted something like this: XX-XX-XXX-XXX, but the length and format depends on the county you live in.
If you pay your property taxes through a mortgage, you may need to contact your lender for a copy of your bill. You may also obtain the number from your county assessor's office. A list of counties with contact information can be found on the Illinois Department of Revenue website .