X12 requires Transaction Control Number to be unique within a Functional Group. So same TCN can be reused within Interchange if it is used in different Functional Groups. Some of HIPAA transactions like 276/277 carry over this requirement. However for 837 transaction, requirement is changed so TCN should be unique within an Interchange, i.e. it cannot be reused within different Functional Groups.
Interchange Control Number does not get reported in any acknowledgments (997/999 use group control number and TCN; 277 Claim Ack uses BHT03).
So why 837 has more strict requirement than X12 and other HIPAA transactions ? What is the business reason for this ?
The "X12 requirement" is in the definition of this ST02 data element, and requires that the TCN be unique across the Functional Group. In developing the 5010 837 Implementation Guides, the workgroup expanded the requirement to the interchange. This does not violate the X12 definition, it does go further. The rationale was that in the environment of health care transactions, with the potential of multiple clearinghouses between the original sender and final receiver, making the number unique at a higher level is an advantage in tracking and researching problems. This was a consensus decision by the developers of 5010, and remained at this level through the X12 and CMS review processes.