Reference

EDI X12 glossary

Plain-English definitions for the X12 vocabulary you'll encounter in partner implementation guides, rejections, and onboarding calls.

ISA

Interchange Control Header. The first segment in any X12 transmission. Holds sender ID, receiver ID, date, time, and the interchange control number. Always 106 characters in 4010 and later.

IEA

Interchange Control Trailer. The last segment in an X12 transmission. Holds the count of function groups in the interchange and a control number that must match the ISA.

GS

Functional Group Header. Groups one or more transactions of the same type (e.g., all 850s in this transmission). Holds sender, receiver, date, and group control number.

GE

Functional Group Trailer. Closes the GS. Holds the count of transactions and the matching group control number.

ST

Transaction Set Header. Marks the start of a single transaction (one 850, one 856, etc.). Holds the transaction set ID code (850, 856, 810, 997) and a transaction control number.

SE

Transaction Set Trailer. Closes the ST. Holds the count of segments in the transaction (inclusive of ST and SE) and the matching transaction control number.

Segment

A single line of EDI data, ending with a segment terminator (typically ~ or a newline). A segment starts with a 2- or 3-character ID (ISA, GS, ST, BEG, REF, PO1, etc.).

Element

A field within a segment, separated by element separators (typically *). Position matters — PO1*1*5*EA means line number 1, quantity 5, unit-of-measure each.

Sub-element

A field within an element, separated by sub-element separators (typically :). Used in composite data elements.

Qualifier

A code that tells the receiver how to interpret the next element. REF*VR*ABC means "ABC is a vendor ID," REF*PO*123 means "123 is a purchase order number." Qualifier codes are defined in the X12 standard and partner implementation guides.

Control number

A unique sequence number used to detect duplicate or out-of-sequence transmissions. ISA, GS, and ST each have their own control number. The control number in the trailer (IEA, GE, SE) must match the corresponding header.

Envelope

The ISA…IEA wrapper around a transmission. Many problems are envelope problems — wrong sender ID, wrong control number, wrong delimiter declaration in the ISA.

850

Purchase Order. Buyer to seller. "Ship me these items."

855

Purchase Order Acknowledgement. Seller to buyer. "I received your PO; here's what I will ship and when."

856

Advance Ship Notice (ASN). Seller to buyer. "Here is what is in the truck, in what cartons, on what pallets." Critical for retailer compliance — late or wrong 856s drive chargebacks.

810

Invoice. Seller to buyer. "Pay me for these items."

820

Payment Order / Remittance Advice. Buyer to seller. "I am paying these invoices."

940

Warehouse Shipping Order. Owner to 3PL. "Ship these items."

943

Warehouse Stock Transfer Shipment Advice. Sender to receiver. "Inventory is being moved between locations."

944

Warehouse Stock Transfer Receipt Advice.

945

Warehouse Shipping Advice. 3PL to owner. "We shipped this."

947

Warehouse Inventory Adjustment Advice.

997

Functional Acknowledgement. Receiver to sender. "I received your transmission and the syntax was valid (or it had these errors)."

999

Implementation Acknowledgement. Like 997 but newer; flags implementation-guide-level errors, not just syntax.

VAN

Value-Added Network. A third-party message-routing service that moves EDI files between trading partners. Examples: SPS Commerce, OpenText GXS, IBM Sterling. Typically charged per kilocharacter.

AS2

Applicability Statement 2. A direct point-to-point EDI transport protocol over HTTPS with cryptographic receipts (MDNs). Often used to bypass VAN per-character fees.

SFTP

SSH File Transfer Protocol. A simpler EDI transport — drop files in a folder. Less metadata than AS2.

MDN

Message Disposition Notification. The cryptographic receipt returned by AS2 when a file is received. Confirms delivery, not business acceptance.

Partner profile

The set of identifiers, qualifiers, and routing details for a trading partner: ISA sender/receiver IDs, GS sender/receiver IDs, AS2 URL, AS2 ID, encryption certificate.

Implementation guide

A partner-specific PDF (or web page) that says "for our 850, REF*VR is required, PO1 must include element 7 (vendor part), and we don't accept SAC segments." Always overrides the X12 standard for that partner.

Chargeback

A fee or deduction the retailer takes from your invoice when you violate a compliance rule — late ASN, wrong UCC-128 label, missing pack list. EDI compliance failures are how big retailers protect their margin.

UCC-128 / SSCC-18

Serial Shipping Container Code. The 18-digit barcode on a shipping carton. Referenced in the 856 ASN at the carton level.

EDIFACT

A different EDI standard maintained by the UN. Used internationally. Not interchangeable with X12, though tools sometimes support both.

Loop

A repeating group of segments inside a transaction. The 850 has loops for line items (PO1 loop), ship-to addresses (N1 loop), etc.

HL

Hierarchical Level. A segment used to express parent/child relationships, especially in 856 ASNs (shipment → order → pack → item).