Legal basis
Electronic invoicing in public contracts is governed by Law 4601/2019, which transposed Directive 2014/55/EU, as amended by Law 4972/2022. The national e-invoice format was set by joint ministerial decision 63446/2021 and the mandatory timetable by decision 52445/2023, as amended in 2024 and 2025. The obligation falls on suppliers: the public sector has had to receive e-invoices since 2019, suppliers have had to issue them in phases since 2023.
The phases
The obligation applies per contracting authority and is triggered for contracts whose award procedure started after the relevant date, not by the invoice date.
| From | Contracting authorities |
|---|---|
| 12 September 2023 | Ministries of Infrastructure and Transport, Digital Governance, Migration and Asylum, the Municipality of Athens, ΕΚΑΠΥ, the National Central Purchasing Authority, Information Society SA, Athens University of Economics, Attiko Metro, ΕΥΔΑΠ, Egnatia Odos |
| 1 January 2024 | The rest of central government: the Presidency, all ministries, decentralised administrations, independent authorities, Parliament |
| 1 June 2024 | All remaining contracting authorities and entities: municipalities, regions, public law bodies, hospitals, universities, state-owned companies |
| 1 September 2025 | Other expenditure of general government not arising from a supply or service contract |
By September 2026 all phases are in force. Any contract with the public sector tendered after 1 June 2024 is invoiced electronically, and tender documents contain an express clause to that effect.
Exemptions
- Minor value contracts up to 2,500 euros (articles 117Α and 327Α of Law 4412/2016) and other expenditure up to 2,500 euros.
- Contracts between public sector bodies and contracts between contracting authorities.
- Project-based contracts of natural persons with general government bodies, since June 2025.
- Contracts performed outside the EU, and certain defence and security contracts.
What the supplier needs
- A certified e-invoicing providerAn e-invoice to the public sector is issued and transmitted only through a provider certified by the General Secretariat for Information Systems and Digital Governance for transactions with the state. B2G certification is separate from the licensing of providers for myDATA, and not every provider qualifies. The tax authority's timologio application and plain PDFs do not meet the requirement.
- The national formatThe invoice follows the European standard EN 16931 in its Greek specialisation, in UBL form. The provider takes care of the technical format; you supply the data.
- The ΑΔΑΜ of the contractThe contract reference field of the invoice carries the ΑΔΑΜ of the contract from ΚΗΜΔΗΣ, the code with the SYMV prefix. For contracts without an ΑΔΑΜ, such as minor value ones, zero is entered. The ΚΗΜΔΗΣ guide explains where to find it.
- The contracting authority's identifiersEvery authority and every unit of it has an identifier on the Peppol network. Ask the finance department for it together with the award, because a wrong identifier means the invoice reaches the wrong body or nobody.
- Transmission and validationThe provider transmits the invoice over the Peppol network to the Interoperability Centre of the General Secretariat, which validates format and mandatory fields and forwards it to the authority. An invoice rejected at validation is not deemed received and the payment deadline does not start.
What changes on 1 October 2026
1 October 2026 is not a new phase of invoicing to the public sector. It is the date on which mandatory e-invoicing between businesses extends to businesses with gross revenue up to one million euros, following the larger businesses that joined in early 2026. A tolerance period runs to 31 December 2026 for those who declare their start in myDATA in time.
For a supplier to the public sector the practical consequence is that the same provider will now also cover invoices to private customers. Check that your provider holds both certifications, for B2G from the General Secretariat and for B2B from the tax authority, so that you do not need two systems.
What goes wrong in practice
- Wrong or missing ΑΔΑΜ. The most common reason for rejection. Use the ΑΔΑΜ of the contract, not of the tender notice or the award decision.
- Invoice addressed to a unit other than the one that signed the contract. Hospitals and large municipalities have many units with separate identifiers.
- Amounts that do not match the contract or the acceptance protocol, especially in partial deliveries.
- Issuing before acceptance. Many authorities reject invoices issued before the acceptance protocol was signed, because the payment deadline runs from acceptance.
Every contract in the GOVADI platform shows its ΑΔΑΜ and the payment orders that follow it, so that you can see whether your invoice has moved to payment without searching ΚΗΜΔΗΣ.
Frequently asked questions
Is e-invoicing to the Greek public sector mandatory?
Yes, for every contract with any contracting authority whose procedure started after 1 June 2024, and earlier for central government. Contracts up to 2,500 euros and contracts between public bodies are exempt.
Can I send a PDF invoice to a municipality?
Not for contracts covered by the obligation. The invoice must be issued through a certified provider in the national format and transmitted over Peppol to the Interoperability Centre. A PDF is not deemed a received invoice.
Which ΑΔΑΜ do I put on the invoice?
The ΑΔΑΜ of the contract, the code with the SYMV prefix that the agreement received when recorded in ΚΗΜΔΗΣ. For contracts without an ΑΔΑΜ, zero is entered.
Does anything change for the public sector on 1 October 2026?
Not directly. 1 October 2026 concerns the extension of mandatory e-invoicing between businesses to those with revenue up to one million euros. Invoicing to the public sector has been mandatory since 2024.
What happens if the invoice is rejected at validation?
It is not deemed received, the payment deadline does not start and it has to be reissued corrected. The most common reasons are a wrong ΑΔΑΜ, a wrong unit identifier and amounts that do not match the contract.