HR-CIUS is the Croatian Core Invoice Usage Specification, the national implementation of the European standard EN 16931. Since 1 January 2026, HR-CIUS has been the mandatory format for B2B e-invoicing in Croatia as part of the Fiscalization 2.0 programme.

HR-CIUS adds Croatian business rules on top of the European standard EN 16931 and Peppol BIS Billing V3. Similar to NLCIUS in the Netherlands and XRechnung in Germany, HR-CIUS concretises the European standard for the Croatian market.

Invoices that comply with HR-CIUS automatically comply with Peppol BIS Billing V3 and EN 16931 as well. The reverse does not apply: a generic BIS 3.0 invoice may not meet the additional Croatian rules.

HR-CIUS sets additional requirements on top of BIS Billing V3:

• OIB (Osobni identifikacijski broj): mandatory identifier for all Croatian parties
• Digital signature: mandatory, linked to the issuer's OIB
• Product classification codes (KPD): mandatory at invoice level
• Payment terms and bank account: mandatory on the invoice

HR-CIUS is inseparably linked to Croatia's Fiscalization 2.0 programme, which combines e-invoicing with real-time fiscalisation at the tax authority (Porezna uprava). Both the sender and the receiver must fiscalise each transaction, enabling the tax authority to perform cross-checks.

Although HR-CIUS is the official format, Peppol BIS Billing V3 invoices are also accepted. Foreign suppliers invoicing Croatian recipients can use BIS 3.0 without having to convert specifically to HR-CIUS, provided the invoice contains the mandatory identifier (OIB).

eConnect supports invoicing to Croatia via the Peppol network. The PSB routes invoices automatically in Peppol BIS Billing V3 and adapts the format based on the recipient's expectations.

• E-invoicing in Croatia
• Peppol BIS Billing V3
• NLCIUS: the Dutch standard
• XRechnung: the German standard
• From semantics to syntax