e-invoicing Greece 2026: the 12 October declaration is the next hard deadline

Athens, 1 September 2026. The Greek tax authority AADE began contacting taxpayers electronically in late August 2026 about their obligations under the second and final phase of mandatory B2B e-invoicing. That outreach exposes a deadline in e-invoicing Greece 2026 beside the known start date of 1 October: to use the transition period you must declare it through myDATA by 12 October 2026. It is not an automatic right but something you claim.

AADE is the Independent Authority for Public Revenue, established on 1 January 2017 and supervised by the Greek parliament, not the Ministry of Finance.

What Changes on 1 October and for Whom

Phase 2 takes effect on 1 October 2026 for businesses with gross annual turnover up to 1 million euro, based on the tax return for the financial year beginning in 2023. Above that threshold the obligation has applied since 2 March 2026.

The scope covers B2B transactions within Greece, B2B transactions with entities outside the European Union, and B2G transactions with public bodies, unless separate legislation already prescribes electronic invoicing there. See our review of enforcement practice across Europe.

The myDATA Declaration Makes the Transition Period Conditional

A transition period runs until 31 December 2026, during which businesses may keep using existing invoicing methods alongside electronic ones. That flexibility is conditional: it applies only to businesses that formally declare through myDATA that they are moving to electronic invoicing, stating 1 October 2026 or earlier as the start date.

The declaration must be submitted by 12 October 2026. Companies that file late, or not at all, face the penalties for late or missing informative returns. Without the declaration of electronic issuance there is no transition period.

1 October and 12 October Are Two Different Dates

Reporting regularly goes wrong here: secondary sources conflate them and some present 12 October as the start date. That is incorrect. 1 October 2026 is the date the obligation takes effect, 12 October 2026 the final date by which the declaration must reach myDATA. The first sets when you fall under the mandate, the second whether the transition period applies.

The Greek Model and the Two Permitted Channels

myDATA, My Digital Accounting and Tax Application, has been the real-time reporting framework for Greek VAT-registered businesses since 2021. The 2026 mandate adds structured invoice exchange: VAT books and invoice data go to myDATA in a prescribed XML format following the European standard EN 16931-1. The invoice then receives a unique registration reference, the MARK, and a QR code for verification against myDATA, which AADE also uses for pre-filled VAT returns. B2G Peppol has been in use in Greece since 2025.

There are exactly two permitted channels: authorised e-invoicing service providers meeting the technical and security requirements set by AADE, known in Greek legislation as an Electronic Data Issuance Provider (EDIP), and the free AADE applications timologio and myDATAapp, which create invoices and transmit them to myDATA.

Commercial providers must be established in Greece and meet financial stability requirements; invoice data may be stored elsewhere in the EU. Your current Peppol Serviceprovider is therefore not automatically an accredited service provider in Greece. An accesspoint alone does not cover a clearance model either: Greece validates in advance through the tax authority, while Peppol is a decentralised four-corner network. See our comparison with the Belgian Peppol approach.

The Greek derogation from Articles 218 and 232 of Directive 2006/112/EC rests on Council Implementing Decision (EU) 2025/502, valid from 1 July 2025 to 31 December 2027. Under ViDA the pre-clearance model must be replaced by January 2035; see ViDA implementation by country.

Penalties and the Obligation to Accept

Issuing an invoice outside the new framework counts as non-issuance. For documents subject to VAT the penalty is 50 percent of the VAT amount on the invoice. For non-VAT transactions fixed penalties of 500 or 1,000 euro apply, depending on the taxpayer’s accounting system.

An acceptance obligation has applied since 2 March 2026: recipients, both businesses and public bodies, must accept e-invoices. Refusal can amount to non-compliance.

e-invoicing Greece 2026: What It Means and What You Should Do Now

For Dutch and Belgian companies with a Greek entity, or issuing Greek invoices from a central ERP, the task is to build the Greek requirements in without breaking order-to-cash.

Checklist for Finance and Accounting

1. Submit the declaration of electronic issuance through myDATA by 12 October 2026, stating 1 October 2026 or earlier as the start date. No declaration, no transition period.
2. Check whether 2023 financial-year turnover sits below 1 million euro, and which entities and flows are in scope from 1 October.
3. Check master data: tax numbers, addresses, legal names, invoice classifications, tax codes and payment details. Data acceptable on a PDF can fail automated validation.
4. Define who handles rejected invoices, within what deadline and along which escalation path.

Checklist for Integrators and Service Providers

1. Verify that the chosen party is an EDIP authorised in Greece; accreditation elsewhere in Europe does not count.
2. Assess whether timologio or the myDATAapp suffices, or whether volume requires ERP integration with an EDIP.
3. Map VAT books and invoice data to the EN 16931-1 XML format and the myDATA classifications, including less frequent document types.
4. Write validation result, MARK, QR code and document status back to accounting and customer records, with exception management for rejections.

The weeks remaining are short for a programme of master data, ERP mapping, provider selection and testing. Putting e-invoicing Greece 2026 on the agenda now starts not with 1 October but with the declaration due on 12 October. Compare Peppol Serviceproviders on support for clearance models such as myDATA.

Sources

1. Athens Times, “Electronic Invoicing: Which Businesses Must Comply Starting October 1”, 27 August 2026
2. vatcalc.com, “Greece B2B e-invoicing 2nd phase October 2026”, 6 August 2026
3. VATupdate, “Greece’s mandatory B2B e-Invoicing enters its second phase in October 2026”, 31 August 2026
4. RTC, “E-Invoicing in Greece: 2026 Key Dates and Requirements”
5. Council Implementing Decision (EU) 2025/502
6. AADE, myDATA