Order Receipt is not a complete web service, but rather a specification of a service that must be exposed as part of a local library system to enable the system to be updated with order receipts from the national ILL infrastructure.
Order Receipt WSDL v1.3 can be found here
Order Receipt XSD v1.3 can be found here
Please note that the WSDL/XSD should be included in the local implementation of the Order Receipt-web service. The URLs above are not to be considered persistent and should therefore not be referenced directly from any services, schemas, or instances of these.