Business Application Header (BAH) — The Identity Card Travelling With the Message

ISO 20022 Beyond the Message

“Sender of what ? Receiver of what ? Which ID identifies the payment instruction, and which ID identifies the business message carrying it? Which message definition is this? Which business service is this conversation using? When was this business message created?”

The Business Application Header , usually shortened to BAH , gives an ISO 20022 business message a consistent place for information about the business message rather than the business transaction body itself.

The official ISO 20022 explanation is very precise: the BAH is itself an ISO 20022 Message Definition in the head.001.001.0x family. It can be combined with another ISO 20022 Message Definition to form a business message. It gathers information such as which organisation sent the business message, which organisation should receive it, the identity/reference of the message and related message-level data in one predictable place, independently of the network used to transport it.

The ISO 20022 catalogue, checked on 11 October 2026 , lists head.001.001.04 — BusinessApplicationHeaderV04 and also head.001.001.02 — BusinessApplicationHeaderV02 . Do not interpret a higher version number as the version required by every service. The BAH overview page still describes V03 documentation approved on 7 March 2022; use the exact catalogue artefact and the receiving service's contract rather than treating that overview date as a universal version mandate.

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