Vehicle Payment Plan Agreement. A vehicle payment plan agreement is a contract between a buyer and seller of a vehicle that agrees to installment payments.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. Identification of the Parties: Clearly state the buyer and seller's full names and addresses. 2. Customize and Download this "Bill Of Sale With Payment Plan". A California motor vehicle bill of sale is part of the vehicle registration process. Use a free template to write your own bill of sale. This is the motor number or serial number required for identification purposes. Payment : The bill of sale document should also state the method of payment used such as installments or in full, cash, check, credit card or bank deposit.