The 855 PO Acknowledgment is the supplier's response to an 850 Purchase Order. It confirms accepted, changed, or rejected line items and communicates any ship date or quantity changes.
BAK
Beginning Acknowledgment — original PO number, acknowledgment type
PO1
Baseline Item Data — accepted line items with confirmed quantity/price
ACK
Line Item Acknowledgment — status code for each line (AC, IP, R)
DTM
Date/Time Reference — confirmed ship date
CTT
Transaction Totals
Triggered by an inbound 850. ACK segment status codes drive downstream order management: AC (Accepted), IA (Item Accepted), R (Rejected), IP (Item in Process).
Ensure BAK03 matches the original PO number from the 850 BEG02. Missing ACK segments are a common compliance failure.