Conditional (C8)
This field contains the identification of the reset/advice to which the current message is related.
This field must not start or end with a slash '/' and must not contain two consecutive slashes '//' (Error code(s): T26).
This field must contain the content of field 20 Sender's Reference of the previous reset/advice which is to be amended or cancelled by this message, or the reference of the telex/fax of the original reset/advice.