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Spotlight PEPPOL BIS Billing 3.0 The EU e-invoicing mandate is here — France Sept 2026, Belgium Jan 2026, Germany 2025.

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X12 855 — Purchase Order Acknowledgment

The 855 is the supplier's formal response to an 850 purchase order. It confirms acceptance, flags changes or notifies rejection — line by line.

Purpose

When a buyer sends an 850, the supplier must produce a business-level acknowledgment (the 997 covers syntax only). The 855 is exactly that: for each line it states whether the item is accepted as is, accepted with change (quantity adjusted, delivery date moved, price corrected), backordered, or rejected. The 855 closes the negotiation phase and clears the supplier to prepare the shipment.

In practice, the 850/855 pair forms the operational contract. Buyer-side ERPs typically reflect the 855 state on the order: if the acknowledgment indicates a partial quantity or a different date, the business user sees this before the shipment goes out.

Envelope structure

The 855 travels in a PR functional group (Purchase Order Acknowledgment). Here is a didactic 855 responding to order PO78901:

x12 example-855.x12 
ISA*00*          *00*          *ZZ*ACMEVENDOR    *ZZ*ACMERETAIL    *260513*1530*U*00401*000000124*0*P*>~
GS*PR*ACMEVENDOR*ACMERETAIL*20260513*1530*1*X*004010~
ST*855*0001~
BAK*00*AC*PO78901*20260513~
REF*VR*VENDOR-ACK-552~
N1*VN*ACME VENDOR INC*92*VEND001~
PO1*1*2*EA*9.99**UP*012345678905~
ACK*IA*2*EA**UP*012345678905~
PO1*2*5*EA*19.50**UP*012345678912~
ACK*IB*4*EA**UP*012345678912~
CTT*2~
SE*10*0001~
GE*1*1~
IEA*1*000000124~

The BAK segment opens the transaction: function code, acknowledgment code (AC = Acknowledge — With Detail and Change, AK = Acknowledge — No Detail or Change), original PO reference, date. Each PO1 is paired with an ACK which carries the line-level status code (IA = Item Accepted, IB = Item Accepted with Quantity Change, IR = Item Rejected, IQ = Item on Hold…).

Common segments

  • Header — ST, BAK (Beginning Segment for PO Acknowledgment), CUR (currency), REF (supplier references), DTM (business dates).
  • Parties — N1 loop for Vendor, Buyer, Ship From, Bill To.
  • Lines — PO1 loop with ACK (line status), PID (description), SCH (revised schedule), DTM (availability date), TXI.
  • Summary — CTT, AMT, SE.

When you'll see it

  • Retail — most vendor compliance programs require an 855 within a contractual SLA (often 24 business hours) after receiving the 850.
  • Manufacturing — used to confirm availability dates when the 850 requests delivery on a specific date.
  • Distribution — key for stock-out handling: an ACK with a "Backorder" code keeps the order open on the buyer side without requiring an 860.

Documentation

The code 855 and the name Purchase Order Acknowledgment are public and listed on x12.org/products/transaction-sets. The detail of qualifiers, loops, and code lists belongs to the proprietary Implementation Guides (TR3); ediverse.io does not redistribute it.