SA Segment (Interchange Control Header) The ISA segment is the envelope for the EDI document, defining communication details between the sender and receiver. ISA01 (Authorization Information Qualifier): 00 – No authorization information present. ISA02 (Authorization Information): Blank – Not used in this document. ISA03 (Security Information Qualifier): 00 – No security information present. ISA04 (Security… Continue reading EDI 850 (Purchase Order) document in X12 format