This is a tutorial on the California residential purchase agreement. OFFER: A. THIS IS AN OFFER FROM________________________________________________________________________("Buyer").You need a bill of sale in California if you're buying or selling a horse or, in many cases, if you register a car that you bought from a private seller. The California Vehicle Purchase Agreement form is a legally binding document used in transactions for purchasing a vehicle in California. California Bill of Sale Forms (3). A California bill of sale is an official document used to record the sale of personal property between a buyer and seller. ("Broker") beginning (date). CAR (California Association of Realtors) residential purchase and sale agreements are widely used in real estate transactions throughout California.