Transfer, Replace, or Change Title To prove vehicle ownership, it's important to have a valid, up-to-date, and accurate Certificate of Title. Complete the new owner information on the back of the certificate and sign it.Bill(s) of sale, if needed to establish a complete chain of ownership. This is the motor number or serial number required for identification purposes. Visit the California DMV's website and download a bill of sale. A bill of sale is a legal document that serves as proof of purchase and, in some cases, records a transfer of ownership — in this case, for a vehicle. Learn about bills of sale in California for animals, vehicles, firearms, and more. The Seller agrees to deliver the Vehicle to Buyer with a current registration and a clear title.