Mandatory e-invoicing is entering its next phase in Greece. From 1 October 2026, the new requirements will apply to businesses included in the second phase of implementation.
This is not simply a change in how invoice data is reported to myDATA. Businesses will need to issue their invoices through one of the approved e-invoicing methods and ensure that all necessary steps are completed within the relevant deadlines.
It is therefore important for businesses to prepare in advance and make sure that the appropriate e-invoicing solution has been selected and all required declarations have been properly submitted.
When does mandatory e-invoicing begin?
For businesses included in the second phase, the new requirements take effect on:
1 October 2026
A transitional period will apply from 1 October to 31 December 2026, with full compliance required from 1 January 2027.
To make use of the transitional period, however, businesses must complete the required procedures on time, with an e-invoicing start date no later than 1 October 2026.
Which transactions are covered?
Mandatory e-invoicing applies, among others, to:
- domestic transactions between businesses (B2B);
- transactions with businesses established in third countries outside the European Union, where the relevant requirements apply;
- transactions with public-sector entitiesB2G).
The requirement does not apply to retail transactions with individual consumers (B2C).
How can electronic invoices be issued?
Businesses have two main options:
1. Through AADE's timologio / myDATAapp
AADE provides its timologio application and its mobile version, myDATAapp, free of charge. Businesses choosing this option are responsible for submitting the required e-invoicing commencement declaration through myAADE
2. Through a licensed e-invoicing provider
Businesses may also choose to work with a licensed e-invoicing provider. In this case, the provider will generally submit the relevant commencement declaration, while the business must review and accept it where required.
Important: ERP and invoicing software
Simply using an ERP system or invoicing software is not sufficient on its own to meet the mandatory e-invoicing requirements.
An ERP system must be properly connected to a licensed e-invoicing provider, or the business must use AADE's timologio/myDATAapp solution.
The key deadline: 11 October 2026
If a business starts using e-invoicing on 1 October 2026, the relevant declaration must be submitted within 10 days, meaning by 11 October 2026.
If e-invoicing begins earlier, the 10-day deadline is calculated from the actual start date.
Submitting the declaration on time is particularly important for businesses wishing to take advantage of the transitional period through the end of 2026.
What Should Businesses Do Now?
With the implementation date approaching, businesses should not wait until 1 October to review their e-invoicing arrangements.
They should confirm in advance:
- whether they fall within the second phase of mandatory e-invoicing;
- which e-invoicing solution they currently use or intend to use;
- whether their existing ERP or invoicing software is properly connected to a licensed provider;
- whether a new declaration or any additional action through myAADE is required;
- whether all relevant declarations and procedures have been completed correctly and on time.
Proper preparation is essential to ensure a smooth transition and avoid compliance issues once the new requirements take effect.
What happens in case of non-compliance?
Failure to issue an electronic invoice through one of the approved methods is treated as a failure to issue an invoice and may result in penalties under the Greek Code of Tax Procedure.
The applicable penalties vary depending on the type of transaction, the accounting system used and whether VAT is involved. Higher penalties may also apply in cases of repeated non-compliance.
AFS supports businesses through the transition
The transition to mandatory e-invoicing requires timely preparation and effective coordination between the business, its accounting processes and its e-invoicing provider or software provider.
AFS – Athens Financial Services is closely monitoring the implementation of the new framework and supporting its clients in preparing for the upcoming requirements.
