If an Information Receiver (provider) submits a 270 Inquiry with an ID that the Information Source (payer) determines is inactive, however, they find other coverage for the same member with a different ID, which is more appropriate based on 1.4.7.1 Item 2 and Item 6:
2100C NM109 = Old (inactive) ID
2100C DTP = dates of inactive plan
2110C EB01 = 6
2120C NM109 = New (active) ID
OR
2100C NM109 = New (active) ID
2100C REF01 = Q4 with REF02= Old (inactive) ID
2100C DTP = dates of active plan
2110C EB01 = 1
2110C EB = 6
2110C DTP = dates of inactive plan
The 005010X279A1 Technical Report Type 3 (TR3) addresses this issue. The element note for data element NM108 in the Subscriber Name (NM1) segment in loop 2100C says that the identifier returned ‘is the primary number that the information source associates with the subscriber.’ This is the active ID. Therefore, a version of your second option is appropriate for the specific scenario you describe (i.e., the information source has identified a different active ID within the context of its search capability and search constraints). Note that the 2100C INS segment is required when acknowledging a change in the identifying element sent on the 270.
2100C NM109 = Active ID
2100C REF01 = Q4 with REF02= Inactive ID
2100C INS with INS03=001 and INS04=25
2100C DTP = dates of active plan
2110C EB01 = 1
2110C EB01 = 6
2110C DTP = dates of inactive plan