Mandatory electronic invoicing is moving to the next phase of implementation and from 1 October 2026 concerns businesses included in Period B.

The change does not simply concern the way documents are transmitted to myDATA. Businesses will need to issue their invoices through the prescribed electronic invoicing solutions and to have carried out the necessary actions in good time.

For this reason, it is important for businesses to contact their accountant or tax specialist in good time, so that they can confirm whether they fall under the new obligation, which solution they will use and whether the required declarations have been completed correctly.

When does mandatory electronic invoicing start?

For businesses of Period B, the obligation starts on:

1 October 2026

A transitional period is provided from 1 October to 31 December 2026, while from 1 January 2027 full compliance with the new regime is предусмотрed.

However, for a business to be able to make use of the transitional period, the required actions must have been completed in good time and the starting date for the use of electronic invoicing must be no later than 1 October 2026.

Which transactions does it concern?

Mandatory electronic invoicing concerns, among others:

  • transactions between businesses in Greece (B2B),
  • transactions with businesses in third countries outside the European Union, where the relevant obligation applies,
  • transactions with public sector bodies (B2G).

It does not concern retail transactions to private consumers (B2C).

How will electronic invoices be issued?

Businesses have two basic options:

1. Through the timologio / myDATAapp application of the AADE

This is the free solution of the AADE. In this case, the business itself must proceed with the relevant Declaration of Commencement of Electronic Issuance of Documents.

2. Through a licensed Provider of Electronic Issuance of Documents

The business may cooperate with a certified electronic invoicing provider. In this case, the relevant declaration is usually submitted by the provider and the business must check and accept the process where required.

Attention to ERPs and invoicing programs

The mere use of an ERP or invoicing program is not in itself sufficient to fulfil the electronic invoicing obligation.

The ERP must operate through the предусмотрed interconnection with a licensed provider or the business must use the timologio/myDATAapp solution of the AADE.

The critical date of 11 October 2026

Provided that the use of electronic invoicing begins on 1 October 2026, the relevant declaration must be submitted within 10 days, that is, by 11 October 2026.

If the business starts earlier, the corresponding 10-day deadline is calculated from the actual starting date.

Timely declaration is particularly important for the ability to make use of the transitional period until the end of 2026.

What should businesses do now?

With the implementation date approaching, businesses should not wait until 1 October to consider the matter.

They need to confirm in good time:

  • whether they fall under the Second period of mandatory electronic invoicing,
  • which electronic invoicing solution they use or are going to use,
  • whether their existing ERP or invoicing program is properly interconnected,
  • whether a new declaration or other action is required in myAADE,
  • whether the relevant declarations have been submitted correctly and on time.

Confirmation with the business’s accountant or tax consultant is essential, so that each case is checked separately and omissions are avoided before the obligation begins.

What is provided in the event of non-compliance?

The non-issuance of an electronic invoice by one of the prescribed methods is treated as non-issuance of an invoice, with the corresponding penalties provided for by the Code of Tax Procedure.

Depending on the type of transaction, the accounting system and the existence of VAT, different fines are предусмотрed, which may increase in the event of recidivism.

AFS alongside businesses in the transition

The transition to mandatory electronic invoicing requires timely review and proper coordination between the business, the accountant and the provider or software supplier.

The team of AFS – Athens Financial Services monitors the changes and supports businesses in the proper preparation and compliance with the new tax and accounting obligations.