Mandatory e-invoicing: what to do before October 1, 2026

From October 1, 2026, electronic invoicing becomes mandatory for business-to-business transactions in Greece, for everyone. You will read plenty of articles rushing you. Here you get the opposite: the dates as they stand today, what applies to you and what does not, and what is worth doing now so you are not doing it under pressure in September.

The dates, plainly

• Phase 1, March 2, 2026: businesses with 2023 turnover above €1,000,000. Already running, with a transition period until May 3, 2026.
• Phase 2, October 1, 2026: everyone else. Which, most likely, means you.

There is also something most articles skip: Phase 2 comes with an adjustment period until December 31, 2026. That does not mean you can leave it for next year; it means you do not need to panic. You do need to have moved, though: invoices issued without an approved transmission method after the deadline count as never issued at all. And that carries a fine of 50% of the invoice’s VAT.

What actually changes

Today you issue an invoice from your software and its data flows to myDATA. Under the new regime, an invoice to another business must be issued and delivered electronically through an approved channel: either a certified e-invoicing provider, or AADE’s free applications (timologio, myDATAapp). You also have to file a declaration of commencement of electronic document issuance before you start. The kind of paperwork that gets forgotten, which is why I am writing it down.

The obligation covers sales to businesses in Greece and to businesses in non-EU countries. Intra-EU transactions remain optional for now.

What does NOT change

Retail receipts are not part of this obligation; they already have their own transmission rules. If your e-shop sells only to consumers and issues only receipts, this wave does not catch you. But if you also issue invoices, to corporate customers, to resellers, to anyone who asks for “an invoice please”, then it applies to you in full.

Your options

• AADE’s free applications. Zero cost, but manual work per document. A sensible choice if you issue a handful of invoices a month.
• A certified provider. A subscription, usually per document or in bundles. This is where most businesses will land.
• A provider connected to your system. The difference from the previous option is not the provider, it is the connection: the order becomes an invoice on its own, without anyone retyping it. If you issue dozens of invoices a month, this is where the change either costs you time or saves it.

There are also tax incentives for the transition, such as full depreciation of the related equipment and software in the year of purchase. Ask your accountant what applies to your case; these things change and I will not pretend to know them better than they do.

What is worth doing now

Nothing dramatic. Three things, in order:

1. Count how many B2B invoices you issue per month. That number decides for you: few means the free apps or a simple provider, many means a connection to your system.

2. Check whether your invoicing software supports a provider, and which one. Most well-known packages already have an answer. If yours does not, better to find out in July than in September.

3. Close the decision before summer ends. In September everyone will be scrambling at once, and both providers and accountants will have a queue. Automation pays off when the volume justifies it, and here the law hands you the reason to measure it.

If your e-shop or your system needs a connection that does not exist off the shelf, that is the work I do. Send me two lines about what software you use and how many documents you issue, and I will tell you honestly whether you need custom work or something ready-made covers you.