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.Customize and Download this "Bill Of Sale With Payment Plan". Selling or transferring ownership of a car, boat or other item of personal property? Easily create, print, and download a Bill of Sale in minutes. Proof of ownership may be a bill of sale, conditional sales contract, out ofstate registration, etc. 4. Seal vehicle deals securely. Use our free template to create a bill of sale with a promissory note for automobiles. A payment plan agreement outlines an installment plan to repay an outstanding balance over a specified time frame.