If field 21R is present in sequence A, and field 28D indicates that more than one message is chained for this request for transfer instruction, the currency code must be the same for all occurrences of field 32B in sequence B of all chained messages.
In case field 23E identifies with a code a sweeping (CMSW), topping (CMTO) or zero balancing (CMZB) operation, the transaction amount in field 32B can equal zero.
In case field 28D indicates that messages are chained, all messages belonging to the same chain must have exactly the same sender's reference in field 20.
In case field 28D indicates that messages are chained, sequence A must be repeated and be identical for all messages belonging to the same chain.