Mandatory
This field contains the reference number of the collection, as shown on the collection instruction.
This field must not start or end with a slash ('/') and must not contain two consecutive slashes ('//') (Error code(s): T26).
If the MT 430 is sent to amend a previously transmitted MT 405 Clean Collection, then:
field 20 of the MT 430 should contain the transaction reference of this MT 405, ie, field 21A of sequence B, and
field 72 of the MT 430 should contain the Sender's reference of this MT 405, ie, field 20 of sequence A.