Greece e-Invoicing: What Changes from October 1, 2026?

Greece’s second mandatory e-Invoicing phase starts on October 1, 2026. Smaller businesses may use a transition period until December 31, but only if the required declaration is filed on time. The Tax Authority has also clarified how the rules apply to the free online invoicing application (timologio) and myDATA app users.

Greece is approaching the second implementation phase of its mandatory e-Invoicing regime. From October 1, 2026, businesses not already covered by the first phase must generally issue their relevant invoices electronically through an approved channel. At the same time, the Tax Authority (AADE) has clarified an important practical question: when businesses using its free online invoicing (timologio) and myDATAapp applications need to file a declaration and when an additional declaration is not required.

The clarification is particularly relevant to smaller businesses because they can use a transitional period between October 1 and December 31, 2026. During that period, qualifying businesses may gradually move to mandatory e-Invoicing while continuing to use their existing invoice-issuance methods, provided they meet the declaration requirements.

This change concerns invoices, not retail receipts issued to final consumers. The Tax Authority’s clarification does not change the existing way B2C retail receipts are issued.

Greece has divided the mandatory e-Invoicing rollout into two implementation periods.

The first phase covered businesses with gross revenue above EUR 1 million, based on their income tax return for tax year 2023. For those businesses, mandatory E-Invoicing has applied since March 2, 2026.

The second phase covers the remaining businesses. According to AADE’s current guidance, mandatory E-Invoicing for this group starts on October 1, 2026.

The rule therefore brings smaller businesses into the mandatory system, but Greece has provided an additional three-month adjustment period.

From October 1 through December 31, 2026, businesses in the second phase may gradually comply while continuing to issue invoices through other permitted methods. This transitional option is not automatic. Businesses wishing to use it must have made the relevant declaration within the required timeframe.

After the transition expires, the ordinary expectation is that invoices within the mandatory scope will be issued exclusively through the permitted electronic channels.

The practical issue clarified by the Tax Authority concerns the relationship between the mandatory e-Invoicing rules and businesses using the online invoicing application (timologio) or myDATAapp.

The Tax Authority provides the free online invoicing application through which businesses can digitally issue invoices and transmit the relevant information to myDATA in real time. The application is intended particularly for businesses without a separate invoicing system or where the existing software does not cover their invoicing needs.

Where a business moves to the Tax Authority applications and issues the relevant invoices exclusively through the online invoicing application (timologio) or myDATAapp from October 1, the specific “Declaration of Commencement of Electronic Issuance of Tax Documents” applicable to other e-Invoicing arrangements is not required in the same way.

However, businesses must still correctly select and declare the applicable transmission channel in accordance with the Tax Authority process. The Tax Authority’s e-Invoicing portal specifically states that businesses must identify whether they use an e-Invoicing Provider or the invoicing application, and selecting the invoicing application also covers myDATAapp.

The distinction is therefore important: the absence of the specific commencement declaration should not be understood as meaning that the invoicing application users have no registration or channel-selection obligations at all.

The declaration becomes particularly relevant for businesses with gross revenue of up to EUR 1 million that want to use the October-December transition.

These businesses may continue using their existing invoice methods alongside e-Invoicing until December 31, 2026, but only if they have timely submitted either the relevant electronic-issuance commencement declaration or the declaration concerning use of the online invoicing application, depending on the selected channel.

In practical terms, a smaller business has two different situations to distinguish.

A business moving fully to online invoicing application or myDATAapp from October 1 does not need the transitional arrangement simply to continue issuing invoices in old ways.

By contrast, a business that wants to continue combining the previous method with the new electronic process during the remaining months of 2026 must ensure that it qualifies for and correctly activates the transition within the prescribed deadline.

Impact on retailers and software providers

For retailers, the October change primarily affects B2B invoicing, including invoices generated from transactions that may originate in stores, e-commerce systems or central ERP environments.

It does not replace or alter the ordinary B2C retail receipt process simply because mandatory E-Invoicing expands to more businesses.

POS and ERP providers should therefore keep the two processes separate. A retail transaction may still generate the required retail receipt under the applicable Greek fiscal rules, while a qualifying B2B transaction may additionally need to follow the mandatory e-Invoicing process.

For software providers, the operational issue is also the correct routing of documents. Systems should know whether an invoice is being issued through an approved Provider, online invoicing application or myDATAapp and ensure that the required data reaches the Tax Authority’s myDATA platform with the appropriate Unique Registration Number (MARK).

What should businesses do before October 1?

Businesses entering the second phase should first determine which E-Invoicing channel they will use: an approved Provider or the Tax Authority’s free online invoicing application/myDATAapp applications.

Those that intend to move fully to the free Tax Authority applications should make sure their invoicing process can operate exclusively through that channel from October 1 and that the correct channel selection has been recorded.

Businesses with 2023 gross revenues up to EUR 1 million that want to continue using their existing invoicing methods during the transitional period should pay particular attention to the October 12, 2026 declaration deadline.

From a retail compliance perspective, the most important issue is not simply whether an invoice reaches myDATA. Businesses need to distinguish the mandatory E-Invoicing channel, the transitional declaration and the separate retail receipt process. Treating all three as the same obligation could lead to incorrect implementation.

The source for this article is the news article published by the DNews regarding electronic invoices. Source

Ivana Picajkić, Medior Legal Consultant at Fiscal Solutions

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