Electronic Invoicing from 1 October: What applies and who must submit a declaration by 12/10

Mandatory electronic invoicing moves from 1 October 2026 into its second implementation period, with the businesses included in it now needing to be prepared for the new invoicing regime.

Shortly before implementation begins, the AADE provided additional clarifications on one point that has raised quite a few questions in the market: the “Declaration of Commencement of Electronic Issuance of Documents”.

Who must ultimately submit it? Who does not need to? And why is 12 October 2026 an important date for specific businesses?

Let us see what applies.

Mandatory electronic invoicing: What applies from 1 October 2026?

From 1/10/2026, the mandatory electronic invoicing regime begins for businesses in the second period.

In practice, it is no longer sufficient merely to transmit the data of an invoice to myDATA. Invoicing must be issued through the solutions provided for electronic invoicing.

Businesses may choose between a licensed Electronic Invoicing Provider and the AADE’s free timologio / myDATAapp applications.

Similarly, the existence of an ERP or other commercial software does not in itself mean that the business has met the new obligation. It must be ensured that the solution used operates in accordance with the prescribed requirements.

What is the transitional period until 31/12/2026?

For businesses in the second period, a possibility of gradual adjustment is provided from 1 October to 31 December 2026.

The transitional period allows, under the prescribed conditions, the temporary continuation of invoicing by the existing permitted methods as well, giving the business more time to complete its transition.

This does not, however, mean that all businesses can simply wait until the end of December. To make use of the transitional period, the relevant conditions must be met.

For whom is 12 October 2026 important?

According to the latest clarifications from the AADE, the deadline concerns businesses in the second period with gross revenues of up to 1 million euros, on the basis of tax year 2023, which wish to make use of the transitional period until the end of 2026.

For these cases, 12 October 2026 is the date requiring particular attention in relation to the required declaration.

Who must submit the Declaration of Commencement of Electronic Issuance of Documents?

This declaration concerns businesses that wish to make use of the possibility of gradual adjustment until 31/12/2026 and to continue, during that period, issuing invoices also by the existing permitted methods.

The process is carried out electronically through myAADE, via the route:

Applications → Tax Services → myDATA → Declaration of electronic issuance of documents via Provider, Self-Provider or the timologio application.

Do you use timologio or myDATAapp? What does the AADE clarify

One of the most important points of the new update concerns businesses that choose the AADE’s free applications.

If, from 1 October 2026, a business issues its invoices exclusively through timologio or myDATAapp, it does not need to submit this declaration in order to make use of the transitional period.

For businesses using Electronic Invoicing Provider Services, the procedure provided for the use of a Provider applies.

What applies to retail receipts and B2C transactions?

Mandatory electronic invoicing does not change the method of issuing revenue documents in retail transactions with end consumers (B2C).

Therefore, the new requirements do not mean that the way retail receipts are issued to private individuals changes accordingly.

What should every business check now?

With the start of the second period now very near, the important thing is for every business to know exactly what applies in its own case.

Before 1 October, it should be clarified which electronic invoicing solution will be used, whether the existing ERP or invoicing software is suitably adapted, whether the business wishes to make use of the transitional period and, above all, whether any declaration or additional action on myAADE is required.

Timely preparation is particularly important, as the required actions are not the same for all businesses.

Not sure what applies to your business?

AFS – Athens Financial Services monitors developments in mandatory electronic invoicing and supports businesses in checking their obligations and properly preparing for the transition to the new regime.

If you do not know whether you must submit a declaration by 12/10/2026, which electronic invoicing solution is suitable for your business or which actions must be completed before the obligation takes effect, contact our team.

📞 210 8317 702 📧 info@afs.gr

Alternatively, complete the contact form and the AFS team will get in touch with you to review your business needs.