Developing global business service delivery platforms for complex services will benefit from a structured design approach that takes into account a variety of requirements including diversity of service domains, different levels of service granularity, service expectations, amongst several others. We propose a model-driven approach that starts with establishing a model to describe business services from the perspective of business people. This Unified Service Model (USM) provides a holistic approach to designing a wide spectrum of services while modeling business services at multiple levels of granularity, from large-grained business functions to finer-grained IT functions. By specifying both the business aspects as well as the operational aspects of a business service, USM supports communication between service providers and service consumers as well as between service providers and service implementers. By leveraging the recursive nature of any service operation model, USM also provides a path for communicating higher-level operational goals to lower-level services. In this paper, we describe the USM meta-model in the context of a healthcare insurance example.