BACS Standard 18
BACS Standard 18 is a file format used to send payment instructions in the United Kingdom.
The format is maintained by the Bankers' Automated Clearing Service, and the detailed specification is available only to subscribers.
Some banks have issued their own specifications for a "Standard 18" file to be imported by their software. These specifications do not necessarily match that issued by BACS; they may impose additional requirements, or change the semantics of some fields.
The file headers and trailers are based on ANSI X3.27.