Return is linked to bill. Vehicle is linked to work order. Preparation includes car wash, fuel fill, and minor repairs such as bulb replacements. There is a vehicle with a given license number. Instances of service invoices are created.
Vehicle is linked to service invoices.
The Payee pays for the Rental. The Payee could be an insurance company or Customer. There is a bill with a given confirmation number. An instance of payment is created. Bill is linked to payment.