The present document is part 6 of the Stage 3 Parlay X 2 Web Services specification for Open Service Access (OSA). The OSA specifications define an architecture that enables application developers to make use of network functionality through an open standardized interface@ i.e. the OSA APIs. The present document specifies the Payment Web Service. The following are defined here: Name spaces. Sequence diagrams. Data definitions. Interface specification plus detailed method descriptions. Fault definitions. Service Policies. WSDL Description of the interfaces.