You'll need to sign the car purchase agreement (or dealer bill of sale), the title, an odometer statement, and sometimes a damage disclosure statement. 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. An Ohio motor vehicle bill of sale is a legal document providing proof of the sale and purchase of a motor vehicle in the State of Ohio. My bank wants purchase agreement or bill of sale before sending out a check to the dealer. What should you include in your vehicle bill of sale?