Concept Definition
What is a CIUS?
A CIUS (Core Invoice Usage Specification) is a national or sector-specific constrained implementation of EN 16931. It may make optional fields mandatory, restrict code list values, or add business rules, but cannot remove any mandatory EN 16931 field. XRechnung and Peppol BIS Billing 3.0 are both CIUS specifications.
What is the difference between a CIUS and an Extension?
EN 16931 defines two customization mechanisms:
- CIUS: Can only restrict the base standard. Cannot add new data elements. Must remain EN 16931 conformant.
- Extension: Can add new data elements beyond EN 16931. Extensions are not EN 16931 conformant and require specific receiver support.
- Example: Peppol BIS Billing 3.0 is a CIUS. ZUGFeRD Extended profile is an extension.
Frequently Asked Questions
- Which CIUS specifications exist in Europe?
- Major European CIUS specifications include Peppol BIS Billing 3.0 (used across 40+ countries), XRechnung (Germany B2G), NLCIUS (Netherlands), CIUS-AT-NAT (Austria), and CIUS-RO (Romania). Each restricts EN 16931 for national or network requirements.
- Does a CIUS invoice validate against EN 16931?
- Yes. A valid CIUS invoice is also a valid EN 16931 invoice by definition, since CIUS can only add restrictions, not remove mandatory requirements. However, an EN 16931 invoice may not satisfy all CIUS requirements if mandatory CIUS fields are absent.