Innovative eCustoms solutions play an important role in the pan-European eGovernment strategy. The underlying premise is interoperability postulating a common understanding of processes, services and the documents that are exchanged between business and government organizations as well as between governmental authorities of different EU member states. This article provides a stringent approach for deriving documents and services from current eCustoms procedures based on the UN/CEFACT standards framework and for embedding these in a service oriented architecture for Collaborative eGovernment. In doing so, we put a special focus on document engineering by applying the UN/CEFACT Core Component Technical Specification (CCTS), a conceptual framework for modeling document components in a syntax neutral and technology independent manner. By relying on CCTS, we want to tackle the challenge of handling different document configurations imposed by divergent national legislations, different customs procedures (export, import, transit, and excise) and different industries. The resulting conceptual model is transferred to XML schema serving as a basis for Web Services design and implementation. These Web Services are designed for seamless interoperable exchange of electronic customs documents between heterogeneous IS landscapes both on business and government side. Beyond the theoretical deduction practical insights are gained from a European research project implementing the artifacts proposed in a real-world setting.