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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

ElementNameDescription
BEG01Transaction set purpose00 = original, 05 = replacement, 01 = cancellation.
BEG03Purchase order numberPrimary business key — must match partner systems and downstream 856/810 references.
BEG05PO dateCCYYMMDD; 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

Frequently asked questions

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