What is EN 16931?
Short answer
EN 16931 is a European standard for electronic invoicing issued on the basis of Directive 2014/55/EU. It determines the semantic data model — what data the e-invoice must contain and what it means (Business Terms, BT). It does not specify a specific XML format or delivery method; this is ensured by implementations such as UBL, CII or Peppol BIS Billing 3.0.
What the invoice must contain
EN 16931 defines mandatory and optional Business Terms and their meaning.
XML addresses other standards
UBL or CII ensure specific writing in XML.
BIS Billing 3.0
Peppol BIS Billing adds its own implementation and validation rules on top of EN 16931.
There is no tax assessment
The standard does not verify the correctness of the VAT regime or the business case.
Conclusion
EN 16931 determines the content and meaning of electronic invoice data; the recording format (UBL/CII) and the delivery method (e.g. Peppol) are handled by another layer of standards.
Not legal advice. Machine-translated answer, not yet manually reviewed. For the exact wording, see the Slovak original.