This Technical Specification defines a uniform structure and meaning for the information that fully represents postal rates for a broad variety of postal products in all mail categories. The postal rates definition is viewed as an important interface between posts and their customers and as such will benefit from standardization. Such representation of postal rates allows automated systems to uniformly use postal rates as they are introduced for new products or updated for existing postal products by postal operators. A postal rate file (PRF) is an XML document, which fully describes postal products rates. It contains all necessary and sufficient information for both postal operators and their customers to efficiently create, respectively acquire, update and process postal product rates. The structure, types and constraints of XML elements in an XML document are defined by an XML schema. The Extensible Postal Rates (EPR) schema is the XML schema that governs Postal Rate Files. This Technical Specification contains a complete description of the EPR schema, its hierarchical structure, information types and semantics of its elements. This Technical Specification neither defines nor constraints how postal rates are created by postal operators but rather provide a powerful and flexible tool that supports efficient rates definition, management and distribution. This Technical Specification does not define communication protocols that can be used by posts to distribute postal rates files to their customers. Suitable communication protocols are typically well known and already standardized (for example: Web Services, File Transport Protocol, email, etc.). The standard also does not define valuation of postal products as applied by postal operators and their customers.