AS 2805.2:2019 PDF
This Standard specifies the message structure, format, content, data elements and values for data elements required for an interface by which card-originated electronic messages relating to financial transactions may be interchanged.
Services of the financial industry include the exchange of electronic messages relating to financial transactions. Agreements on application specifications are generally at a private level. This Standard is designed as an interface specification enabling messages to be exchanged between systems adopting a variety of application specifications. The application specification can remain at a private level. As long as messages conform to the interface format, as prescribed in this Standard, in order for interchange to take place, all other features of applications can be altered as required.
This Standard uses a concept whereby each data element is assigned a position indicator in a control field which is known as a “bitmap”. The presence of a data element in a specific message is indicated by a one (1) in the assigned position; the absence of a data element is indicated by a zero (0) in the assigned position.
Message formats used in individual systems are subject to the commercial relationships between the parties contracting to each system. The data formats specified in this Standard are designed to ensure compatibility between systems.