An Illinois motor vehicle bill of sale documents the purchase and sale of a motor vehicle between a private seller and buyer in the State of Illinois. Complete and mail the Notice of Sale form.(attached to the bottom of the title) to the. In the upper section, sellers are required to input details about the vehicle, including make, model, year, VIN (Vehicle Identification Number), and mileage. The Illinois bill of sale form approves the exchange of a financial consideration for an item of property into a text register. This is the motor number or serial number required for identification purposes.