The Greek EN 16931 CIUS is Greece's national version of Peppol BIS Billing 3.0, for e-invoices to Greek public bodies. It keeps the Peppol syntax and adds Greek fields and rules, such as the budget and contract references and, for Greek suppliers, the MARK number from myDATA. Invoices travel through Peppol to a single endpoint run by GSIS. Dedicated Klarbon support is planned, not available yet.
What does the Greek CIUS add?
| Field or rule | What it holds |
|---|---|
| BT-11 project reference | budget type 1, 2 or 3 and a reference, separated by a vertical bar |
| BT-12 contract reference | the contract number (ADAM) |
| Buyer identifier | the contracting authority's label code |
| MARK | the myDATA unique registration number, required for Greek suppliers |
| GR-R rules | Greek checks, for example a Greek seller VAT number starts with EL |
| Property | Value |
|---|---|
| Basis | EN 16931, Peppol BIS Billing 3.0 |
| Specification identifier | the Peppol BIS Billing 3.0 identifier |
| Endpoint | 9933:997001671, the National Interoperability Centre (KED) |
| Authority | GSIS, the General Secretariat for Information Systems and Digital Governance, the Greek Peppol Authority |
GSIS describes the format, the legal basis in law 4601/2019 and the role of myDATA in its guide (GSIS guide). Its February 2026 instructions for foreign sellers set out the endpoint and the fields a supplier must fill (GSIS instructions). The GSIS e-invoice page lists the newer Greek editions of the guide and the legislation (GSIS).
Greek CIUS, Peppol BIS and myDATA
| Greek CIUS | Peppol BIS Billing 3.0 | myDATA | |
|---|---|---|---|
| What it is | an e-invoice to a public body | an e-invoice | tax data |
| Rules | EN 16931, Peppol, Greek | EN 16931, Peppol | AADE |
| Goes to | KED through Peppol | any Peppol receiver | AADE |
What does Klarbon do with Greek invoices?
Dedicated support, including the Greek rules, is planned, not available yet. Klarbon opens and checks Peppol BIS Billing 3.0 invoices, which the Greek CIUS narrows. Check results are against the EN 16931 and Peppol BIS rules, in beta; see the invoice checker. Klarbon does not send invoices through the Peppol network.
Related
Frequently asked questions
What is the Greek CIUS?
The Greek national data format for e-invoices to public bodies. It narrows Peppol BIS Billing 3.0, which itself narrows the European standard EN 16931, so a valid Greek invoice is also valid Peppol BIS and EN 16931.
Where do I send an e-invoice to a Greek public body?
Through a Peppol certified service provider, to the single Peppol endpoint of all Greek contracting authorities, 9933:997001671, at the National Interoperability Centre (KED) of GSIS.
Which fields must a Greek public sector invoice fill?
Among others, the project reference (BT-11) as budget type and reference, the contract reference (BT-12), the buyer identifier of the contracting authority, and for Greek suppliers the MARK number from myDATA.
Does a foreign supplier need a MARK number?
The Greek rules require a MARK when the supplier is Greek. A supplier without a Greek tax number sends through a Peppol certified service provider and follows the GSIS instructions for foreign sellers.