855
X12 855 transaction set, the purchase-order acknowledgment of the order cycle.
Definition
The 855 acknowledges an 850. Its header opens with the BAK segment (Beginning Segment for Purchase Order Acknowledgment), carrying the purpose code, the acknowledgment type (AC accept with change, AD accept without change, RJ rejected) and the PO number. Each line is echoed in an ACK loop with line-by-line status.
Origin
Defined by ASC X12 (ANSI-accredited standards body since 1979) in subcommittee X12C; the 855 belongs to functional group PR (Purchase Order Acknowledgment).
Example in context
ST*855*0001~ then BAK*00*AD*PO-12345*20260620~ — original acknowledgment, order accepted without change.