MT 501 Network Validated Rules

C1 

If the message is a cancellation, ie, Function of the Message (field 23G) is CANC, then a reference to the previous message must be specified in the Linkage section, ie, field :20C::PREV must be present minimum once in one and only one occurrence of A1; consequently, in all other occurrences of A1, field :20C::PREV is not allowed that message (Error code(s): E08).

Sequence A if field :23G: is...	then field :20C::PREV is...
CANC	Mandatory in one occurrence of subseq. A1, and not allowed in all other occurrences of subseq. A1
NEWM	N.A.

Sequence A if field :23G: is...	then in minimum one occurrence of subsequence A1 field :20C::PREV is...
CANC	Mandatory (note: it does not need to be present in all occurrences of A1)
not CANC	Optional