An 855 · Purchase Order Acknowledgment is the seller's business answer to an 850 · Purchase Order: yes, no, or yes-with-changes — line by line, with quantities, prices, and ship dates the seller is actually committing to. It is not a receipt. The receipt was the 997 · Functional Acknowledgment. The 855 is a promise, and most order disputes start with a team treating those two documents as the same thing.
I run SignalEDI, and yesterday's piece covered what a 997 proves (structure parsed) and what it does not (business acceptance). The 855 is the document that closes that second gap — when it is sent, read, and acted on. Too often it is one of the three.
What is an 855 · Purchase Order Acknowledgment?
It is the X12 transaction set a seller returns after reviewing a buyer's 850 · Purchase Order in their own business system. Where the 997 is generated by a translator, the 855 is generated by an order process: someone — or some rules engine — looked at item availability, pricing, and the requested ship window, and decided what the seller can actually do.
The header carries the acknowledgment type in the BAK segment: accept the order as-is, accept with changes, reject, or accept with conditions. The detail loops then go line by line, typically in ACK segments, stating for each line the quantity acknowledged, the unit of measure, the promised ship date, and a status code that says whether that line is accepted, backordered, rejected, changed, or accepted with a substituted item.
That line-level granularity is the whole point. An order is rarely all-yes or all-no. Two lines ship Friday, one line is short by half, and one line carries a price that changed last month. The 855 is where each of those facts gets said, in machine-readable form, while there is still time to react.
How is an 855 different from a 997 and an 856?
These three get confused constantly, so keep the layers separate. A 997 · Functional Acknowledgment says the file parsed — translator to translator, no business meaning. An 855 says the seller reviewed the order and is committing (or not) to specific lines, prices, and dates — business system to business system. An 856 · Ship Notice / ASN, sent later, says what actually went on the truck.
Read in sequence, they answer three different questions: Did you get it? (997) Will you do it, and on what terms? (855) Did you do it? (856, followed by the 810 · Invoice for what you now owe). A team that only watches the first and third is flying blind in the middle — exactly where a shorted line or a moved date could still be fixed with a phone call instead of a chargeback.
What do buyers actually do with an 855?
A disciplined buyer reconciles it against the original 850 automatically. Every difference is an exception: quantity acknowledged lower than quantity ordered, price acknowledged different from price expected, date acknowledged later than date requested, line rejected outright. Each exception needs a decision — accept the change, source the shortfall elsewhere, renegotiate — and the value of the 855 is that it surfaces those decisions days before the shipment would have failed silently.
The undisciplined version is just as common: the 855 arrives, gets filed, and nobody diffs it against the order. Then the partial shipment shows up, the three-way match between the 850, the 856, and the 810 · Invoice breaks, and accounting inherits a problem that operations could have solved a week earlier. The document did its job. The process around it did not.
What should sellers get right when sending one?
Send it fast. An acknowledgment that arrives after the goods ship is archaeology, not communication — most trading partner agreements expect it within a day or two of the order. Acknowledge what you will actually do, not what the order asked for: copying the requested quantities and dates into the 855 when the warehouse already knows better converts an honest shortfall into a broken promise. And use the status codes properly per line instead of rejecting a whole order because one line is in trouble — buyers can work with a partial truth; a blanket rejection forces a re-order cycle nobody has time for.
Price deserve special care. If the acknowledged price differs from the buyer's expected price, that difference will detonate later at invoice matching, with interest in the form of deductions. Saying it in the 855 is a disagreement; hiding it until the 810 is an ambush.
What happens when no 855 comes back at all?
Silence here means something different than a missing 997. A missing 997 usually means a technical problem. A missing 855 often means the order is sitting unreviewed in someone's queue — received, parsed, and ignored. Buyers should age unacknowledged orders the same way they age unacknowledged files: an expectation window per partner, an alert when it passes, and a human follow-up while the ship date is still recoverable. Sellers should treat the 855 not as EDI overhead but as the cheapest customer-service message they send — it is the one that says "we saw your order, and here is the truth about it."
Frequently asked questions
Is an 855 required for every order?
That depends on the trading partner agreement. Many retail and distribution programs require it; some partners accept a subset of status responses. What is never optional is the underlying act — reviewing the order and communicating exceptions. The 855 is just the structured way to do it.
Can an 855 change an order?
It records the seller's terms; whether a change takes effect depends on the partner agreement and the buyer's response. An 855 with changes is an offer to proceed on those terms, not a unilateral amendment — which is why buyers need a step that accepts or contests the changes, not just a filing cabinet.
How does the 855 relate to the 865?
The 865 · Purchase Order Change Acknowledgment / Request is the companion used when the buyer initiates a change via an 860 · Purchase Order Change Request. Same idea, opposite direction: whoever changed the deal, the other side answers in a structured document.
The pattern across this series is simple: each EDI document answers exactly one question well, and trouble starts when a team asks it a different one. The 855's question is "will you do it, and on what terms?" Getting that answer early, line by line, is what turns an order from a hope into a plan — and it is the reconciliation discipline we build SignalEDI around.
— Chris, founder of SignalEDI
