X12 segment reference
ST — Transaction Set Header
The ST segment identifies the X12 transaction set (850, 856, 810, 997) and assigns the ST control number used in acknowledgements.
ST segment facts
- ST01 identifies the business document type — parsers route 850 traffic differently from 856 or 810.
- ST02 control numbers must be unique within each GS functional group to keep 997 acknowledgements unambiguous.
- HIPAA transaction sets add ST03 implementation convention references that retail-only guides often omit.
What the ST segment does
ST opens each transaction set inside a functional group. ST01 is the transaction set identifier; ST02 is the control number partners reference in 997 AK2 loops.
Loop: Once per transaction set
Key elements
| Element | Name | Description |
|---|---|---|
| ST01 | Transaction set identifier | 850, 856, 810, 997, etc. |
| ST02 | Transaction set control number | Must be unique within the GS group; echoed in 997 AK2. |
| ST03 | Implementation convention | Optional for retail; required for HIPAA (e.g. 005010X222A1). |
Example ST segment
ST*850*0001~
Parse and validate samples with the free EDI validator or send JSON via the JSON→X12 mapping guide.
Related reference
FAQ
Frequently asked questions
Partners correlate AK2 acknowledgement loops to ST02 control numbers from your outbound document.