X12 validator
Paste any 850, 855, 856, 810, 997 or 824. It reports the document type, every
segment with its element count, and whether the envelope would survive a partner's parser.
What it checks
The envelope rules that cause most group-level rejections:
- ISA present, IEA present — an interchange without both ends is discarded whole.
- ST and SE control numbers agree — a mismatch rejects the transaction set.
- SE01 equals the segment count from ST through SE inclusive. This off-by-one is the most common generator bug.
- ISA has 16 elements — fixed width, and the sixteenth is the element separator itself.
- CTT present for item documents — 850, 855, 856 and 810 carry an item count; a 997 does not.
What it cannot check
Whether the values are legal for that partner. Required segments, code lists, qualifiers and label rules live in the implementation guide, and no generic validator can know them. A document can pass here and still be rejected on a qualifier the guide mandated.
If it fails
Fix in this order, because each step invalidates the next: envelope, then segment order, then element values. Resend the whole transaction set rather than the failing segment, and keep the partner's response file.