EDI 855 - Purchase Order Acknowledgment
The EDI 855 is the supplier's formal response to a purchase order - confirming acceptance, flagging changes, or rejecting lines. It's one of the most compliance-critical documents in retail EDI, with chargebacks triggered for late or missing acknowledgments.
✦ What It Does
The EDI 855 Purchase Order Acknowledgment travels from supplier back to buyer in response to a received 850. It confirms that the supplier received the PO and communicates their intent: accept as-is, accept with modifications, or reject specific lines. Most major retailers require 855 transmission within 24 to 48 hours of 850 receipt, and failure to acknowledge is itself a compliance violation subject to chargeback.
The 855 mirrors the structure of the 850 it references. The BAK (Beginning Acknowledgment) segment opens the transaction with the PO number from the original 850's BEG03, plus a purpose code and acknowledgment type. The transaction then uses PO1 loops - one per line - each carrying the original line number, the acknowledged quantity, and a line-level acknowledgment code (IA = item accepted, IB = item not accepted, IC = item partially accepted, IP = item on back-order). Suppliers use the ACK segment within each PO1 loop to provide granular per-line responses including quantity adjustments and schedule dates.
Where the 855 adds value beyond simple confirmation is in communicating changes: a supplier might acknowledge 8 of 10 units on a given line due to inventory constraints, shift the ship date by 3 days, or substitute a pack size. These changes, documented in the 855, become the agreed-upon version of the order for downstream documents - if the supplier ships 8 units and the 856 matches the 855's acknowledged quantity, no discrepancy chargeback is triggered at the DC.
⚡ When It's Triggered
- An 850 is received from a retailer and the supplier's order management system auto-generates the 855 within the compliance window (typically 24 hours).
- A supplier's inventory check reveals a short-quantity situation on one or more PO lines - the 855 is generated with partial acceptance codes and reduced quantities so the buyer can plan accordingly.
- An item on the PO is discontinued or on back-order - the supplier uses the 855 to reject that line (IB) and prevent a compliance failure from shipping a substitute without authorization.
- A PO ship date falls within a fulfillment window the supplier cannot meet - the 855 proposes a revised ship date that the buyer can accept or escalate.
- A buyer's price on the 850 differs from the supplier's agreed cost - the 855 can flag the price discrepancy in an ACK segment before the goods ship, avoiding AP disputes at invoice matching.
Who Uses EDI 855
Retail Suppliers
Every supplier trading with a major retailer via EDI must send 855s. The retailer's compliance scorecard tracks acknowledgment rate and timeliness. Suppliers with consistently late or missing 855s face vendor compliance fines and risk losing ordering preference. High-volume suppliers may be transmitting hundreds of 855s daily across multiple retail trading partners.
Manufacturing
Manufacturers receiving 850s from industrial buyers or OEM customers use the 855 to confirm production feasibility. When a 850 arrives with a delivery date that conflicts with current capacity, the 855 is the formal mechanism to propose an alternative ship date before committing to fulfillment.
Distribution
Distributors acting as suppliers to retailers send 855s confirming availability from their warehouse stock. Distributors with sophisticated WMS integrations can fire the 855 automatically after an ATP (available-to-promise) check against on-hand inventory, providing real-time availability confirmation without manual intervention.
Grocery Suppliers
In grocery, the 855 is particularly important for promotional orders. When a retailer sends a 850 for a promotional event, the supplier's 855 either confirms they can support the promotional volume or communicates allocation constraints early - before the promotional window opens and shelves go empty.
Key Segments & Data Elements
BAK: Beginning Acknowledgment
Opens the 855 and references the original PO. BAK01 = transaction set purpose code (00 = original, 05 = replace). BAK02 = acknowledgment type: AC = acknowledged, AD = acknowledged with detail changes, AK = acknowledged with changes, RJ = rejected. BAK03 = PO number (must match BEG03 of the 850). BAK04 = date of acknowledgment. BAK09 = transaction type code.
PO1: Line Item
Mirrors the PO1 from the 850. PO101 must match the original line number from the 850. PO102 carries the acknowledged quantity - if the supplier can only fulfill 6 of 10 ordered units, PO102 = 6. PO103 = UOM. PO104 = unit price (if different from PO, this signals a price change). Product qualifiers in PO1 echo the 850's identifiers.
ACK: Line Item Acknowledgment
Appears within the PO1 loop to provide granular line-level status. ACK01 is the line-item status code: IA = item accepted, IB = item not accepted, IC = item accepted - changes made, ID = item not available, IP = item on back-order, IS = item accepted - buyer's requested ship date not met. ACK02 = acknowledged quantity. ACK05/06 = proposed ship date. Multiple ACK segments can appear per PO1 for split shipments.
DTM: Date/Time Reference
At header level, DTM010 confirms the acknowledged ship date. At line level within the PO1 loop, DTM002 provides a line-specific delivery date. If the supplier is proposing a different ship date than the buyer requested in the 850, DTM in the 855 communicates the proposed change before it becomes a delivery exception.
MSG: Message Text
Free-form text segment used to communicate exceptions or context that code-based segments cannot capture. Common uses: explaining a back-order reason, providing a vendor reference number, noting a substitute item being proposed. MSG content is typically routed to a buyer's exceptions queue for review.
CTT: Transaction Totals
Closes the 855 with the total line item count. CTT01 must equal the number of PO1 loops in the acknowledgment. If the supplier is partially acknowledging a 10-line PO with 8 accepted and 2 rejected, the 855 still carries 10 PO1 loops (2 with IB status) and CTT01 = 10. Mismatched CTT counts trigger functional acknowledgment errors.
Related Transaction Sets
Purchase Order
The 850 that the 855 is responding to. Every 855 must carry the original PO number in BAK03. The buyer's order management system matches incoming 855s to open 850s by this reference. If the PO number doesn't match, the 855 will fail validation and may not update the buyer's system.
Purchase Order Change Request
If the buyer needs to modify the PO after reviewing the 855 (e.g., accepting the supplier's proposed reduced quantity), they send an 860. Alternatively, if the supplier's 855 proposes changes the buyer cannot accept, the 860 may be used to assert the original requirements.
Ship Notice / Manifest (ASN)
After the 855, the next supplier-generated document is the 856. The 856 should reflect the quantities acknowledged in the 855 - not the original 850 quantities if changes were made. Retailers match 856 quantities against 855 acknowledged quantities, not against the original 850.
PO Change Acknowledgment
The 865 is a supplier-generated acknowledgment to a buyer's 860 change request. Where the 855 acknowledges the original 850, the 865 acknowledges modifications. Trading partners using both 860 and 865 maintain a documented change history for every order.
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