ISO/IEC 15459-5:2014 specifies a unique string of characters for the identification of individual returnable transport items (RTIs). The character string is intended to be represented in a bar code label or other automatic identification and data capture (AIDC) media attached to the item to meet management needs. To address management needs, different classes of identities are recognized in the various parts of ISO/IEC 15459, which allows different requirements to be met by the identities associated with each class.

The rules for the identification of RTIs, with the identity being relevant for the complete lifecycle of the item, are defined and supported by example.