Clearly print or type all information, except signatures. Vehicles Purchased in a Private Sale.We will be addressing how to fill out a bill of sale form for the sale of a car so let's get started with this guide to filling out a bill of sale form. A bill of sale is a legal document that outlines the purchase of property between a buyer and seller. It commonly includes both parties' information. Use our NY bill of sale forms to prove the transfer of ownership of property from seller to buyer in the state of New York. A detailed description of the process of writing a bill of sale when transferring ownership of a car to a buyer.