Greece: The final e-invoicing wave starts on 1 October

What is changing?

From 1 October 2026, Greece’s mandatory e-invoicing rules extend to the remaining businesses in scope. Invoices must be issued through an authorised e-invoicing provider or AADE’s free timologio and myDATAapp tools. Invoice data is transmitted to AADE’s myDATA platform.

An adjustment period runs until 31 December 2026 for eligible businesses. The conditions depend on how the business issues its invoices.

Why it matters

This is a reason to contact customers with Greek operations and review their actual invoice flow. A customer may know the deadline but still need to establish which entities are affected, which issuance channel they will use and who handles failed transmissions.

Start with these customer questions:

– Which Greek entities and transactions are in scope?
– Will invoices be issued through an authorised provider or AADE’s free tools?
– Does the ERP produce the data needed for that route?
– Who monitors myDATA transmission and resolves errors?
– Is the customer planning to use the adjustment period?
– Has the local finance or tax team confirmed any declaration requirements?

One detail to check carefully

AADE clarified the declaration rules on 22 September 2026. A business using timologio or myDATAapp needs a declaration if its gross revenue was up to €1 million in the 2023 tax year and it wants to use the adjustment period while continuing to issue invoices through existing methods. In that case, the declaration can be submitted until 12 October 2026.

A business issuing invoices exclusively through timologio or myDATAapp from 1 October does not need that declaration. Separate declaration rules apply when using an e-invoicing provider. Ask the customer to confirm the requirements for its chosen route with its local tax team.

Talking point

“Greece’s next e-invoicing phase starts on 1 October. Shall we check which of your Greek entities are affected, how their invoices will be issued and whether the data reaches myDATA correctly? That will show us where you need a process change or further local advice.”

What should partners do next?

Contact affected customers and arrange a short review with their finance and IT teams. Map the invoice flow from ERP to the chosen issuance channel and myDATA. Agree who checks transmission results and who resolves errors.