Purchase Order Acknowledgment
The X12 855 is the supplier's formal response to an 850 Purchase Order, confirming, changing, backordering, or rejecting each line item.
In this guide
855 PO Acknowledgment moves from Supplier / Manufacturer / Vendor to Buyer / Retailer / Distributor (Seller → Buyer) via AS2, SFTP, VAN. The interactive diagram below traces every business and technical step the message passes through — press Play Flow to watch it travel, or click any step for detail.
How it works
How 855 PO Acknowledgment Works
Sender
Supplier / Manufacturer / Vendor
Receiver
Buyer / Retailer / Distributor
Direction
Seller → Buyer
Standard
ANSI ASC X12
Version
005010
Transport
AS2 / SFTP / VAN
Business Purpose
Order Management
Sender — Supplier / Manufacturer / Vendor
EDI Transmission
855
Purchase Order Acknowledgment
ANSI ASC X12 004010 / 005010
Receiver — Buyer / Retailer / Distributor
Related transaction flows
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Ask EDI AI →855 PO Acknowledgment workflow. Steps: Review Incoming PO, Determine Line Status, Generate 855 EDI, Send to Buyer, Receive EDI, Reconcile Against 850, Review Discrepancies. Transmitted from Supplier / Manufacturer / Vendor to Buyer / Retailer / Distributor via AS2, SFTP, VAN, following ANSI ASC X12 004010 / 005010.
Overview
Gives the buyer visibility into whether the order was accepted as-is before goods ship, reducing surprises at receiving.
Sender
Supplier / Manufacturer / Vendor
Receiver
Buyer / Retailer / Distributor
Direction
Seller → Buyer
Standard / Version
ANSI ASC X12 004010 / 005010
Segment structure
Key segments that make up this transaction set:
| Segment | Name | Purpose |
|---|---|---|
| BAK | Beginning Segment for PO Acknowledgment | References the original PO number and acknowledgment type. |
| PO1 | Baseline Item Data | Restates the line item being acknowledged. |
| ACK | Line Item Acknowledgment | States accepted/changed/rejected quantity and reason. |
| DTM | Date/Time Reference | Confirms ship or delivery dates for the line. |
Interactive example
Click any segment below to see its business meaning.
ST
This is an envelope or control segment. Select a highlighted segment on the left (shown in green) for a full business explanation.
View raw EDI
ST*855*0001~
BAK*00*AC*PO-2024-88213*20230915~
PO1*1*100*EA*25.00*PE*VP*SKU-10293*IN*44921~
ACK*IA*100*EA**20230920~
PO1*2*250*EA*4.50*PE*VP*SKU-38810*IN*44987~
ACK*BP*100*EA**20230925~
CTT*2~
SE*8*0001~Mapping example
A representative field-level mapping from a common source system into this transaction:
| Source | Source Field | Target Field |
|---|---|---|
| Order Management System | line.confirmed_qty | ACK02 (Quantity) |
| Order Management System | line.status | ACK01 (Line Item Status Code) |
| Order Management System | line.revised_ship_date | ACK05 (Date) |
Validation rules
- BAK03 must reference a PO number the supplier has actually received.
- Every PO1 loop from the original 850 should have a corresponding ACK response.
- ACK01 status codes must come from the agreed code list (IA, IB, IC, IR, RD, etc.).
- Quantity in ACK02 cannot exceed the originally ordered quantity unless explicitly allowed by the trading partner agreement.
Common errors & troubleshooting
Buyer system shows order as "unacknowledged" despite an 855 being sent
Cause: BAK03 PO number formatting (leading zeros, dashes) doesn't match the original 850 exactly.
Fix: Normalize PO number formatting on both sides before comparison.
Backorder dates rejected by buyer's inbound validation
Cause: ACK05 date is earlier than today's processing date.
Fix: Add a validation rule requiring revised dates to be in the future relative to transmission date.
Related articles
Frequently asked questions
It's not required by the X12 standard itself, but most retail and grocery trading partner agreements require it as proof the order was reviewed before shipment.
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