All 223 rules the European e-invoicing standard defines, in plain language, grouped by what actually went wrong.
The standard publishes its rules as machine readable Schematron, and the error text it ships is written in the vocabulary of the specification. Precise, and close to useless to the person who has to fix the invoice this afternoon. Every entry here answers what to change rather than only which rule failed.
Grouped by symptom rather than by where a rule sits in the spec, because that is how people arrive. Each rule keeps its own anchor, so a link to a specific identifier lands on it directly.
Something the invoice must carry is missing
The VAT on the lines does not reconcile with the breakdown
A value is not in the fixed list the standard allows
The numbers on the invoice do not add up
An amount has more than two decimal places
A field became required because of something else you sent
Drop a Factur-X or ZUGFeRD file into the free validator and it names every rule that fails, with the explanation from this page attached to each one. The EN 16931 rules run in your browser, so the invoice is never uploaded. The ISO PDF/A-3, XRechnung and PEPPOL BIS checks need a server and are a separate opt in that says so.
Validate an invoice, no signupThese pages cover the EN 16931 semantic rules. The checks on the PDF container itself, the embedding and the profile metadata are ours rather than the standard's, and the validator explains each one where it reports it.
