The Business Message Reject <3> message can reject an application-level message which fulfills session-level rules and cannot be rejected via any other means. Note if the message fails a session-level rule (e.g. body length is incorrect), a session-level Reject <3> message should be issued.
The only exception to this rule is when a transport other than the FIX session protocol is being used (transport independence). An appropriate reject message of the given session protocol or the Business Message Reject <3> message should be used instead.
See the session-level Reject <3> message
It should *NOT* be used in the following situations: