Service consumers are increasingly becoming aware of QoS and service subscriptions. Service providers (SPs) are also recognizing the opportunity to generate revenue by bundling services in packages and providing them to customers. Standardization bodies have begun to address requirements of charging and usage accounting management as SPs are increasingly relying on them. Federated accounting management concept stems from these developments. It specifically supports the requirement of SPs to co-operate in a federated manner and share the revenue. It also supports the requirements of charging and billing being subcontracted to a third-party. This paper proposes that standard-based interfaces and shared information model, and a well-accepted development methodology are keys to enabling co-operation between SPs. It presents a requirement analysis and a federated accounting management system architecture, which are based on the recommendations laid down by TMForum, IPDR, OMG and IETF organisations. The architecture supports mediation, rating, charges aggregation, settlement, and online billing.