Glossary Term

CIUS

A CIUS (Core Invoice Usage Specification) is a national or sector-specific extension of EN16931 that adds requirements while maintaining compliance with the European standard.

Quick Facts

purpose
National/sector adaptations
full name
Core Invoice Usage Specification
defined in
EN16931

Definition

What is a CIUS?

CIUS (Core Invoice Usage Specification) is a mechanism defined in EN16931 that allows countries or sectors to add requirements on top of the core standard while remaining compliant.

Think of EN16931 as the "base layer" and CIUS as "add-ons" that enforce additional rules.

How CIUS Works

A CIUS can:

  • Make optional fields mandatory

  • Restrict the allowed values in a field

  • Add validation rules

  • Specify which syntax to use

    • A CIUS cannot:

  • Remove core requirements

  • Change the semantics of fields

  • Add new fields (extensions do that)

    • Major CIUS Implementations

    CIUS Country Key Additions
    ------------------------------
    XRechnung Germany Leitweg-ID mandatory, BR-DE rules
    Peppol BIS International Peppol-specific rules
    SI-UBL Netherlands Dutch B2G requirements
    CIUS-AT Austria Austrian requirements

    Validation

    When validating an invoice:
    1. First check EN16931 core rules
    2. Then check CIUS-specific rules