X12 segment reference
BEG — Beginning Segment for Purchase Order
Reference for the X12 BEG segment in EDI 850 purchase orders: PO type, PO number, and order date fields developers map first.
BEG segment facts
- BEG03 purchase order number is the primary correlation key for 855 acknowledgements, 856 ASNs, and 810 invoices.
- BEG01 transaction purpose codes determine whether the 850 is new, changed, or cancelled — retailers reject wrong codes.
- SignalEDI maps BEG fields to JSON purchaseOrderNumber and orderDate on outbound 850 API payloads.
What the BEG segment does
BEG is the business header for EDI 850 purchase orders. It carries the PO number partners use for matching, invoicing, and ASN correlation.
Loop: Once per 850
Common transaction sets: 850
Key elements
| Element | Name | Description |
|---|---|---|
| BEG01 | Transaction set purpose | 00 = original, 05 = replacement, 01 = cancellation. |
| BEG03 | Purchase order number | Primary business key — must match partner systems and downstream 856/810 references. |
| BEG05 | PO date | CCYYMMDD; timezone and cutoff rules vary by retailer. |
Example BEG segment
BEG*00*SA*PO-1042**20250609~
Parse and validate samples with the free EDI validator or send JSON via the JSON→X12 mapping guide.
Common BEG errors
- PO number format differs from partner spec (leading zeros, max length)
- BEG01 purpose code not accepted for the retailer program
Related reference
FAQ
Frequently asked questions
Yes for standard retail 850 implementations. It is the anchor segment partners validate first.