Factur-X EN16931: your invoice is probably not compliant (and you don't know it)
php
dev.to
Most invoicing solutions claim Factur-X compliance. Few actually pass all three validation levels. The three levels Factur-X conformity requires passing all of these: XSD validation — XML structure is syntactically correct Schematron validation — EN16931 business rules are respected PDF/A-3 validation — the PDF document is archivable with the XML correctly embedded Where most solutions fail PDF/A-3 is the real problem. Common PHP PDF libraries — Dompdf, TCPDF