This Technical Specification defines a mechanism for the unique identification of individual receptacles. It specifies the method of construction of the identifier, referred to as the receptacle asset number, and defines one required and a number of optional methods by which this identifier can be associated with (affixed to) the receptacle itself.The receptacle asset number is defined in accordance with the specification of ISO/IEC 15418 data identifier number 5B, which defines a Receptacle Asset Number or container identifier constructed in accordance with the hierarchical principles defined in ISO/IEC 15459.The specification also identifies a number of receptacle attributes, or characteristics, which it may be useful to communicate between parties making use of the receptacle concerned.A coded representation of one of these attributes - equipment qualifier - is integrated into the structure of the receptacle asset number. The others are not defined in detail in this document. Precise definitions and encoding formats for them will be developed over time, as a result of practical experience of use of the specification. The definitions will be included in an appropriate reference specification, such as UPU standards S25 [17] and M82 [10], which serve as baseline definition documents for attributes used in postal industry communications about postal items, mail aggregates and receptacles.The application of this specification is voluntary in the sense that receptacles are not required to be individually identified.NOTE 1Not all receptacles need to have a receptacle identifier. In particular, in today's environment, mailbags and disposable trays are not normally identified explicitly - rather their contents are. Many posts are, however, starting to individually identify more valuable receptacles and this practice is expected to spread, including to trays, as the advantages of being able to individually track and control receptacle movement become more appa