EDI has its own vocabulary, and encountering a vendor compliance guide or trading partner specification for the first time can feel like reading a foreign language. This glossary covers the six core X12 transaction sets that handle the majority of B2B commerce, plus the terminology you will encounter when setting up EDI for the first time.
The Six Core Transaction Sets
850 — Purchase Order
The 850 is sent by a buyer to a supplier to initiate an order. It specifies what is being ordered, in what quantity, at what price, for delivery where and when. The PO number on the 850 becomes the reference identifier that links every subsequent document in the transaction chain.
855 — Purchase Order Acknowledgment
The 855 is sent by the supplier back to the buyer after receiving an 850. It confirms whether the order can be fulfilled as requested, partially fulfilled, or must be declined. Some trading partners allow line-by-line acceptance or rejection. Most retail compliance programmes require the 855 within a specific time window — often 24 hours of receiving the 850.
856 — Advance Ship Notice (ASN)
The 856 is sent by the supplier when goods leave the warehouse. It details exactly what is on the truck: pallet and carton hierarchy, SSCC barcode numbers, item quantities, and carrier information. The buyer uses the 856 to prepare their receiving dock and pre-populate their warehouse management system before the shipment arrives. Late or inaccurate 856s are the most common source of retail chargebacks.
810 — Invoice
The 810 is sent by the supplier to request payment for shipped goods. It references the original PO number and matches line-item quantities and prices from the 850. The buyer's accounts payable system matches the 810 against the 850 and 856 automatically — any discrepancy flags for review before payment is released.
997 — Functional Acknowledgment
The 997 is a technical receipt — sent by the receiver of any EDI document back to the sender — confirming that the document was received and that it passed structural validation. It does not mean the business content was accepted; it means the EDI file was well-formed. A 997 with an "accepted with errors" status means something in the document failed validation rules and needs correction. Every EDI document you send should generate a 997 in response.
820 — Payment Order / Remittance Advice
The 820 is sent by the buyer to the supplier to communicate payment details — which invoices are being paid, any deductions or adjustments applied, and when funds will be remitted. It allows the supplier's AR team to close out open invoices automatically without manually matching payments to bills.
Key Supporting Terminology
- ISA/GS envelope — the outer wrapper of every X12 EDI file, containing sender/receiver identification and control numbers
- Segment — a line within an EDI document, identified by a two- or three-character segment ID (e.g. BEG for Beginning Segment of a PO, PO1 for a line item)
- Element separator — the character used to separate data elements within a segment (commonly an asterisk *)
- SSCC — Serial Shipping Container Code, an 18-digit GS1 identifier printed on carton and pallet labels and referenced in the 856
- ISA qualifier — a code identifying the type of trading partner ID being used (e.g. 01 for DUNS, ZZ for mutually defined)
- VAN — Value Added Network, a third-party routing service for EDI documents
- AS2 — Applicability Statement 2, a secure real-time internet transport protocol for EDI