X12 275 NM101 (Entity Identifier Code): Format, Values, and Testing Notes
NM101 is only two characters, but it's the code that tells the receiving system whose name it's about to read. In a 275 built around the patient, get this wrong and the identity check downstream is comparing the wrong record entirely.
NM101 is the first element of the NM1 segment — a code that identifies which party this occurrence of NM1 describes. In a 275 attachment transaction, the value QC marks the occurrence as representing the patient whose records are attached.
Valid code values
Example
A synthetic NM1 using entity code QC to mark this occurrence as the patient, Bayo Oyelaran. Synthetic data only.
Where this trips people up
Test data generated by copying an NM1 example from a different transaction type sometimes leaves a provider or payer entity code in place instead of QC, since the segment structure looks identical either way. The file still validates syntactically, but any downstream logic that filters specifically for the patient occurrence never finds one, and the attachment ends up with no confirmed patient identity attached to it at all.