The 865 is the seller’s side of order changes. Its full X12 name, purchase order change acknowledgment/request – seller initiated, covers two uses. Most often it answers a buyer’s PO change (EDI 860), confirming line by line whether the supplier accepts the new quantity, price or date. It can also start a change from the seller’s side, for example when a supplier can only ship part of an order or needs to move a delivery date.
In the order flow, the 865 sits between the change and the shipment: purchase order, PO acknowledgment, PO change, PO change acknowledgment, then advance ship notice. Like the 855, it references the original PO number and carries a status for each line, so both systems end up with the same version of the order before goods move.
Without a clear 865, buyers can’t tell whether a change was accepted, ignored or only partly applied. Fewer trading partners support the 865 than the 855, so changes are often confirmed by email, outside the transaction record. That gap shows up later as three-way match failures, disputed invoices and claims and deductions when the goods received don’t match what the buyer believes was ordered.