ISA/GS Segments
ISA / GS Segments Explained
Every X12 interchange starts with an ISA (Interchange Control Header) segment and ends with IEA. Within each interchange, one or more GS functional groups wrap the actual transaction sets.
| Element | Position | Description | Example |
|---|---|---|---|
| ISA06 | 6 | Interchange Sender ID (your company) | SENDERID |
| ISA08 | 8 | Interchange Receiver ID (partner) | RECEIVERID |
| ISA13 | 13 | Interchange Control Number (unique) | 000000001 |
| ISA16 | 16 | Sub-element separator | > |
| GS02 | 2 | Application Sender Code | SENDERID |
| GS03 | 3 | Application Receiver Code | RECEIVERID |
| GS06 | 6 | Group Control Number | 1 |
| ST01 | 1 | Transaction Set Identifier Code | 850 |
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