If you invoice other businesses in Greece, electronic invoicing is no longer optional. It is being phased in through the tax authority's myDATA platform, and one of the two deadlines has already passed. Here is the plain version: what changed, the dates that actually matter, what you have to do, and where automation takes the dull part off your hands.

What changed

Greece received EU approval to require structured B2B e-invoicing (Council Implementing Decision (EU) 2025/502, in effect from 1 July 2025 to 31 December 2027). In practice this means a B2B invoice is no longer just a PDF you email. It is a structured electronic document that is transmitted to myDATA, gets a unique identifier (a UID) back, and only then goes to your customer. The tax authority sees the invoice as it is issued, rather than months later in a report.

The dates that matter

  • 2 March 2026: mandatory for businesses with gross revenue above €1 million (for fiscal year 2023). A transition period with softer enforcement ran until 3 May 2026, so for large companies this is already live.
  • 1 October 2026: mandatory for everyone else, including small businesses and sole proprietors. A transition period runs to 31 December 2026. If you are a typical Greek SME, this is your date, and it is close.

Sales to other EU countries stay optional for now; the mandate targets domestic B2B (and sales to non-EU businesses).

What you actually have to do

For each covered invoice, you need to issue it in the structured format, send it to myDATA, receive the UID, and deliver it to your customer. You also need to receive structured e-invoices from your suppliers. You have three main routes:

  • A certified e-invoicing provider (πάροχος). The simplest path for most companies: the provider handles the format, the myDATA transmission, and the delivery.
  • The AADE Timologio app. A free government tool for low invoice volumes. It works, but it is manual.
  • Direct integration via the myDATA REST API. Your own accounting or ERP software talks to myDATA directly. This is where a custom build pays off if your volume is high or your setup is specific.

Where automation actually helps

The compliance box is the easy part. The cost that quietly adds up is the daily data work around it, and that is what automation removes:

  • Reading incoming invoices. Supplier e-invoices still need to be checked, coded, and matched to purchase orders and payments. Software can read them and do the first pass, leaving your accountant the exceptions.
  • Matching and reconciliation. Lining up invoices, payments, and bank entries is repetitive and rules-based, which is exactly what automation is good at.
  • Chasing and flagging. Late payments, mismatches, and missing UIDs can be flagged automatically instead of found by hand at month end.
  • Connecting your tools. Most of the pain comes from data being copied between your invoicing tool, your accounting system, and your bank. Wiring those together is usually the highest-value, least glamorous win.

None of this replaces your accountant. It removes the gathering and re-keying so the people who matter spend their time on judgment, not data entry. This is the same idea we cover in our practical guide to AI automation for Greek businesses.

How we think about it

If the October 2026 date applies to you, the first step is not buying software in a panic. It is mapping how an invoice actually moves through your business today, from issue to myDATA to your accounting to your bank, and finding the one step that eats the most time. We start there, prove a fix on your real data, and only then connect it end to end. Everything runs on EU-region hosting and stays GDPR-clean, with a person kept in the loop on anything that affects the books.

If you are not sure what the myDATA mandate means for your specific setup, that is a short, free conversation, and exactly the kind of question we answer before any project starts.