A seller initiates this transaction set to acknowledge receipt of a purchase order change or to request changes to an existing purchase order. Sent by the supplier to the buyer, it uses the BCA (Beginning Segment for Purchase Order Change Acknowledgment) segment to establish context, along with POC (Line Item Change) segments in the detail section to specify modifications to individual line items. Supporting segments such as CTP (Pricing Information), DTM (Date/Time Reference), and ACK (Line Item Acknowledgment) allow the seller to detail pricing adjustments, effective dates, and acceptance status of proposed changes. The transaction set accommodates multiple line items with extensive detail loops, including product descriptions via PID (Product/Item Description), quantity schedules via SCH (Line Item Schedule), and party information via N1 (Name) loops for shipping locations or other entities involved.

Consider a scenario where TechSupply Corp. receives a purchase order change from RetailChain Inc. requesting a quantity increase and expedited delivery for laptop components originally ordered for a specific date. TechSupply responds with a 865 transaction set confirming the quantity adjustment in a POC loop, updating the pricing with a CTP segment to reflect volume pricing, and including an SCH segment with an accelerated delivery date. The seller uses an ACK segment within the POC loop to indicate acceptance of the change, along with a DTM segment specifying when the revised shipment will occur. If additional fees apply for expedited handling, TechSupply includes SAC (Service, Promotion, Allowance, or Charge Information) segments to itemize the charge transparently.