What changes from 1 October 2026
The mandatory e-invoicing rollout is organised in two implementation periods. The first covered businesses with gross revenue above €1,000,000, based on the 2023 income-tax return, and became mandatory from 2 March 2026.
For the remaining businesses, mandatory e-invoicing starts on 1 October 2026.
From 1 October to 31 December 2026, gradual compliance is available under specific conditions, including a timely declaration and a start date for the relevant e-invoicing services no later than 1 October 2026.
Licensed provider or IAPR applications
Businesses can comply through a licensed e-invoicing provider or the free timologio / myDATAapp applications of the Greek Independent Authority for Public Revenue (IAPR/AADE).
A commercial or accounting ERP on its own is not an accepted e-invoicing issuance method. It can form part of the operating solution, but compliant electronic issuance must use one of the prescribed channels.
Electronic invoices are transmitted automatically to myDATA and receive the mandatory Unique Registration Number (MARK).
Why this is not only a software project
Technical activation is only one part of the transition. The business also needs a clear answer to when an invoice is created, by which system, under which series and document type, and how the transaction is ultimately reflected in myDATA and the accounting records.
Five checks before go-live
1. Issuance and transmission channel
Decide whether the business will use a licensed provider, timologio/myDATAapp or an allowed combination, and how existing systems feed the final process.
2. Document types and series
Map standard invoices as well as advances, credit notes, cancellations, special charges and any other flows relevant to the business model.
3. myDATA mapping
Document series, classifications and tax treatment should reconcile with accounting records, VAT and statutory reporting. The objective is not merely successful transmission, but consistent digital tax data.
4. Credits, cancellations and exceptions
Test the scenarios that most often create discrepancies before mandatory go-live.
5. Roles and ownership
Define who issues, who reviews tax mapping, who monitors transmission failures and who coordinates with the provider or software vendor.
Connecting compliance with the operating process
Through Digital Tax Operations, Looma can support invoice-flow mapping, myDATA mapping, accounting/tax coordination with ERP or provider, pre-go-live testing and post-go-live reconciliations.
For recurring accounting and tax support, the e-invoicing process also connects to Accounting & Tax and the ongoing reconciliation of myDATA, VAT and accounting records.
This Brief is for information only and reflects the published IAPR/AADE framework as of the update date. Application to a specific business requires review of its actual transaction model, systems and obligations.