A vehicle bill of sale in Illinois is used to document the purchase and sale of a car between a private seller and a buyer. Get Illinois bill of sale forms and learn how to transfer ownership of vehicles, boats, firearms, and other personal property from one party to another.A bill of sale is a legal document that records the transfer of ownership of an asset to a second party in exchange for money. (iSeeCars) A vehicle bill of sale is an important legal document when a used car's ownership transfers between two people. This is the motor number or serial number required for identification purposes. A bill of sale will detail a transfer of property or sale of items between a seller and buyer. This type of document serves as legal evidence. A bill of sale is a document that verifies you've sold your car and provides basic information about the vehicle and the terms of the sale. A bill of sale refers to a legal record in the form of a written document that highlights the details of a specific transaction.