Mandatory
If the MT 754 is sent to the Issuing Bank, this field contains the documentary credit number assigned by the issuing bank.
If the message is sent to a bank other than the issuing bank, this field contains either the documentary credit number assigned by the issuing bank, or another reference meaningful to the Receiver.
This field must not start or end with a slash '/' and must not contain two consecutive slashes '//' (Error code(s): T26).