TRADACOMS Parser

Decode a TRADACOMS interchange (GS1 UK) segment by segment, 100% client-side. ORDHDR, ORDERS, INVFIL, INVOIC, DLHEAD, SLSRPT — STX/MHD/MTR/END walk, counter cross-checks.

How it works

TRADACOMS is the UK EDI standard developed in 1982 by the ANA (Article Number Association, now GS1 UK). It is still the dominant format in UK retail — Tesco, Sainsbury's, Asda, M&S and Morrisons all use it daily, even in 2026. The format is flat: each line is an ASCII segment of the form TAG=element1+element2+…, terminated by an apostrophe '. Composite element components are separated by :. A release character ? escapes the next byte.

The parser tokenises the interchange while honouring the release character, then extracts:

• STX — Start of Transmission (file header): application authority, sender, recipient, date/time, interchange reference.
• A sequence of messages delimited by MHD (Message Head) and MTR (Message Trailer), with the segment count carried in the MTR.
• END — End of Transmission, with the segment count for the entire file.

Interchange structure

STX=ANAA:1+5012345000004:LEEDS+5012345678907:HEAD OFFICE+260518:113000+12345'
MHD=1+INVFIL:9'
TYP=0700+DETAILED INVOICES'
SDT=5012345678907:LEEDS+1234'
CDT=5012345000004:HEAD OFFICE'
FIL=12345+1+260518'
MTR=6'
MHD=2+INVOIC:9'
CLO=5012345000004:HEAD OFFICE'
IRF=INV00001+260518'
ILD=1+5012345678907:EAN+12+EA+CASE+1500+18000'
STL=1+1+18000+3600+21600'
TLR=21600+3600+18000'
MTR=7'
END=15'

Common messages

The parser ships metadata for the six most-used types in practice:

• ORDHDR — Order Header. File header accompanying one or more ORDERS messages.
• ORDERS — Purchase Order. Order lines (OLD — Order Line Detail) with quantity, EAN/GTIN, agreed price and delivery date.
• INVFIL — Invoice File. File header accompanying one or more INVOIC messages.
• INVOIC — Invoice. Note: same 6-letter type id as EDIFACT INVOIC but a completely different segment structure. Invoice line (ILD), VAT sub-totals (STL), totals (TLR).
• DLHEAD — Delivery Head, header for delivery messages (DELHDR / DELDET — Delivery Header / Detail).
• SLSRPT — Sales Report. Periodic statement from a retailer to a supplier listing units sold per SKU per delivery point. Heavily used by UK grocery for vendor-managed inventory.

Delimiters and escapes

Delimiters in TRADACOMS are fixed:

• Segment terminator: ' (apostrophe).
• Element separator: +.
• Component separator: :.
• Release character (escape): ?. Prefix a delimiter to make it literal: ?+ ≡ +, ?: ≡ :, ?' ≡ ', ?? ≡ ?.
• Decimal mark: . (dot).

Limits

• The parser does not validate the syntax of amounts, dates or EAN/GTIN codes inside elements. Only the envelope structure is checked.
• The mandatory segment lists displayed per message type are indicative: the GS1 UK Manual v9 has gone through several UPDATEs (through 2013) and some operators use proprietary variants.
• TRADACOMS has dozens of other messages (PIIH, GENRAL, PRDTRA, UTLBIL, COREOR…) that this parser tokenises correctly but without dedicated metadata.
• Transport via VAN or FTP, AS2 wrapping and compression controls are out of scope: the parser starts from the plain-text content.

Privacy

Related documentation

• TRADACOMS — overview of the standard, its history and its UK ecosystem.
• EDIFACT — the international standard that was meant to replace it but never succeeded on the UK retail side.
• GS1 UK — the official source of the spec: gs1uk.org.