RFI 1139 clarifies that Transaction Control Number should be unique within interchange for 837 transaction.
How case with miNonexed 837 transactions within same interchange should be handled? i.e. when single interchange has functional groups for institutional, professional and dental 837 transactions; should transaction control numbers be unique in regards to transaction type (P, I or D) or should they be unique independently of transaction type?
This is explicitly addressed in the note on ST02 in all three version 5010 837 TR3s. The note states "The number must be unique within a specific interchange [ISA-IEA], but can repeat in other interchanges."
The transaction set control number must be unique within an interchange independently of the transaction type. This applies whether the transaction sets in the interchange are all of the same type (i.e. P, I, or D) or whether they are a mix of types.