EDI 855: The Purchase Order Acknowledgment, Explained

The EDI 855 is the Purchase Order Acknowledgment. It is the supplier's reply to a buyer's 850 purchase order, telling the buyer which lines are accepted, which are backordered, which have changed in price or quantity, and which are rejected. It closes the loop on whether an order will actually be fulfilled as requested.

Why the 855 matters

Without an acknowledgment, a buyer who sends a PO is left guessing. Did the supplier receive it? Can they fill it? Is the price still valid? The 855 answers these questions before goods ship, so the buyer can react early - find an alternate source for rejected lines, adjust expectations on backorders, or approve price changes. In tightly run supply chains, a fast and accurate 855 prevents expensive surprises at the dock.

The order acknowledgment cycle

1. Buyer sends an 850 purchase order.
2. Supplier replies with an 855 acknowledgment, line by line.
3. If changes are significant, the buyer may send an 860 purchase order change, and the supplier responds with an 865.
4. When goods ship, the supplier sends an 856 and then an 810 invoice.

The key segments of an 855

BAK - Beginning Segment for Purchase Order Acknowledgment

The header. It carries the acknowledgment type and references the original PO. BAK*00*AC*PO-99831*20240116 means an original acknowledgment, status AC (acknowledge with detail), for purchase order PO-99831, dated 2024-01-16.

PO1 - Baseline Item Data

Restates the line items being acknowledged, mirroring the PO1 lines from the original 850 so the buyer can match them.

ACK - Line Item Acknowledgment

The segment that carries the actual status of each line. A code says what is happening: IA item accepted, IB item backordered, IR item rejected, IC item accepted with changes. ACK*IA*100*EA means the line is accepted for 100 each.

CTT and SE

Control totals and the transaction trailer, as in other X12 documents.

A simplified worked example

ST*855*0001~
BAK*00*AC*PO-99831*20240116~
PO1*1*100*EA*12.50**UP*012345678905~
ACK*IA*100*EA~
PO1*2*50*EA*8.75**UP*012345678912~
ACK*IB*30*EA~
CTT*2~
SE*8*0001~

In plain English: the supplier acknowledges purchase order PO-99831. Line 1 is fully accepted for 100 units. Line 2 is partly backordered - only 30 of the 50 requested units are available now.

Common pitfalls when reading an 855

• Missing the ACK status. The PO1 restates what was ordered, but the ACK is what tells you the supplier's answer. Read the ACK, not just the PO1.
• Assuming silence means acceptance. A line with no acknowledgment status should be investigated, not assumed accepted.
• Overlooking accepted-with-changes. An IC status means the supplier changed something - often price or date - which the buyer needs to approve.

Frequently asked questions