Croatia’s Fiskalizacija 2.0 B2B e-invoicing mandate, explained

Since 1 January 2026, Croatia requires structured electronic invoices for domestic B2B transactions between VAT-registered taxpayers established in Croatia. A PDF attached to an email is not enough: the invoice has to be a machine-readable XML document built to the European standard EN 16931 and Croatia’s national rules, HR-FISK 2.0, and its data has to be reported in real time to the Tax Administration. This regime is the Fiskalizacija 2.0 (Fiscalization 2.0) project.

What the mandate requires

For in-scope B2B transactions, the supplier must issue a structured electronic invoice, deliver it to the buyer, and report the fiscally relevant data to the Tax Administration in real time. “Structured” means the invoice data lives in a defined XML model — not pixels in a PDF and not a flat image. In practice that means an invoice built to the EN 16931 core data model and Croatia’s HR-FISK 2.0 national restriction, carried in the UBL 2.1 syntax. A testing phase ran from 1 September 2025 ahead of the mandatory start.

Who is in scope

The B2B mandate targets VAT-registered taxpayers established in Croatia invoicing each other domestically. From 1 January 2027, the issuing obligation is expected to extend to further entities — such as sole traders, liberal professions, and public bodies not registered for VAT. Because the boundaries — non-established suppliers, exempt flows, and edge cases — are defined in law and updated by the Tax Administration, treat the summary above as orientation, not a determination: check your specific situation with the authority or your accountant.

The format: HR-FISK 2.0 on top of EN 16931

Croatia’s format is HR-FISK 2.0 — a national CIUS (Core Invoice Usage Specification) layered on top of EN 16931-1:2017. A CIUS takes the European core invoice model and adds its own mandatory fields and code-list constraints, and HR-FISK 2.0 uses the UBL 2.1 syntax (CII is also part of EN 16931). So an HR-FISK 2.0 invoice is always EN 16931 core compliant, but the reverse is not automatic — the national rules ask for more than the core alone. See what EN 16931 is for the core model and the UBL vs CII distinction.

How Fiskalizacija 2.0 works (Peppol-based exchange plus real-time reporting)

Croatia combines a four-corner exchange with continuous transaction control (CTC). Invoices move between sender and receiver through Peppol-style access points using the AS4 protocol, while the fiscally relevant data is reported to the Tax Administration in real time for outbound invoices, with a reporting window for inbound ones. This differs from Romania’s pure central-clearance model: in Croatia the tax authority sits in the reporting path, not necessarily in the delivery path of every invoice. Producing a correct invoice file, exchanging it, and reporting it are separate jobs.

Where Slipstack fits — and where it does not

Slipstack is on the document side of that split, not the platform or reporting side. From one JSON call it can:

• Generate an EN 16931 core invoice in UBL or CII syntax, or a Factur-X / ZUGFeRD PDF with the XML embedded.
• Validate the EN 16931 core business rules for free before you send anything, with the EN 16931 / XRechnung core validator.

What Slipstack does not do: it is not connected to the Croatian Tax Administration or its fiscalization platform, it is not a certified access point, it does not exchange or report invoices, and it does not register you with the system. It also covers the EN 16931 core, not the additional HR-FISK 2.0 national rules — so a core-valid invoice from Slipstack is a correct starting point, but your accounting software, integrator, or fiscalization provider is responsible for full HR-FISK 2.0 conformance, exchange, and real-time reporting. For what a mandated routing platform is, see what is a PDP.

Related: Romania mandate · Belgium mandate · France mandate · Germany mandate · EN 16931 explained.