Odoo and myDATA: setting it up properly, from the document type to the MARK number.

myDATA is the platform of AADE, the Greek tax authority, for electronic books. Every document you issue from Odoo reaches it as a set of data, and AADE gives it a MARK, the number that identifies it.

AADE’s technical description sets out what each document carries:

• your VAT number and the number of the installation (branch) that issues it;
• the customer’s VAT number and country;
• the document type, its series and its sequential number;
• its lines, with amounts, VAT and an income classification for each;
• the payment method.

Odoo already knows most of this: the customer, the amounts, the VAT. Three things it doesn’t know on its own: which myDATA type each document is, which classification each line gets, and which installation it comes from. We set these up once, with your accountant, and from then on every invoice carries them.

The same AADE interface also works the other way: it brings in the documents others issued to you, meaning your supplier invoices. More on those below.

Software can send invoices to myDATA in two ways. One is directly, with the company’s own credentials on AADE’s interface. The other is through a licensed provider, which signs the invoice, sends it to myDATA and to the customer, and returns the MARK.

For invoices, the first way is closing. Sending straight from your software is allowed until 31 January 2027. From 1 February 2027, invoices to businesses, to customers outside the EU (retail excepted) and to the public sector leave only through a provider or AADE’s free apps.

If your Odoo sends straight to myDATA today, whatever module it uses, that has to change before 31 January 2027. Odoo itself stays; what’s added is the connection to the provider. We build it with eInvoice Link, an add-on inside Odoo: you issue the invoice as always, eInvoice Link checks it, sends it to the provider and brings back the MARK and QR code.

We are not an e-invoicing provider. We work with licensed providers and connect Odoo to them.

Every document in myDATA has a type, with a code set by AADE. In the Odoo we set up, nobody picks the type by hand on each invoice: it follows from the journal the document is issued in and the customer’s fiscal position. That way every common case gets the right type automatically.

The table shows the usual cases for a trading company; AADE has many more types, for self-billing, rent, purchase deeds and more. Your accountant confirms the type for each of your cases before we set it up.

Retail receipts are not part of mandatory e-invoicing. They can come from a cash register, as today, or through a provider instead. Delivery notes have their own timetable: from 1 January 2027 the receipt of goods is recorded too; see digital delivery notes.

Every invoice line in myDATA carries an income classification: a category and a type that say what kind of income it is. A sale of goods to another business in Greece is usually classified with the category «Έσοδα από Πώληση Εμπορευμάτων» (income from sales of goods) and the type E3_561_001 (wholesale sales to businesses). A retail sale to a consumer takes the type E3_561_003 (retail sales to private customers).

In Odoo nobody fills this in line by line. The classification follows from the product or income account and the type of customer, with rules we set once with your accountant.

Expense classifications are the other side: they say what kind of expense each invoice you receive is. Your accountant usually does them. Decide early whether that continues or whether they come from purchases in Odoo, so they aren’t done twice.

Every document in myDATA must have a series and a sequential number. In Odoo, an invoice gets its number when it’s confirmed, and numbering restarts each year unless you change its format. You set the format on the first invoice of each period, and every change is logged on the invoice.

So we set up one journal per series you issue, with a numbering format your accountant agrees. If you move from other software mid-year, Odoo can continue that year’s numbering or start a new series; your accountant decides. Gaps in the numbering, from cancellations or deletions, are flagged by Odoo, so you see them first.

Branches need care. In myDATA every document states which installation issued it, using the number the installation has in AADE’s register; head office is 0. If you also issue from a second shop or warehouse, we set up a separate series for each installation, with the right number.

An invoice that has a MARK isn’t corrected by editing it in Odoo. It’s corrected with a new document, usually a credit note. A credit note for a specific invoice is “related”: it carries the original invoice’s MARK. In the Odoo we set up, you issue it from the original invoice and the MARK follows.

We close off the two most common mistakes in hastily configured Odoo: credit notes issued freely, which reach myDATA unrelated to the original, and invoices reset to draft or deleted after they were sent. A few users may issue credit notes, and nobody may touch an invoice that has a MARK. Cancellations follow AADE’s and the provider’s rules, never a deletion in Odoo; your accountant confirms what to do in each case.

If the connection to the provider drops, or the provider’s to AADE, the invoice must be sent again within one day. That can’t depend on someone in the office remembering. With eInvoice Link the invoice waits its turn and is resent on its own as soon as the connection is back, once, and a console shows what left, what is waiting and why. See it step by step in how an invoice travels.

Since 2 March 2026 every business in Greece must accept its suppliers’ invoices electronically. Their data is already in myDATA, and it can come into Odoo instead of being typed. With the Greek suite for Odoo, supplier documents are matched with your purchases in Odoo. Those still arriving as PDF or paper can be read by AI, with every line checked.

Tests run on a copy of Odoo connected to a test environment, not the live one; AADE has its own test environment for myDATA, so test documents never reach your books. With your accountant, we issue one example of each case you have:

1. a sales invoice and a services invoice, with every VAT rate you use;
2. a related credit note carrying the original’s MARK;
3. an invoice to a business in another EU country and one outside the EU, if you have such customers;
4. an invoice from each branch, with the right installation number;
5. an invoice with a discount and many lines, to see that totals and VAT match on the invoice and in myDATA;
6. an invoice with the connection cut on purpose, to see it wait and resend.

For each, check three things: the MARK came back, the QR code prints on the invoice, and the type and classification are the ones you agreed.

How the rest of Odoo is set up first, from company details to users, is in our guide to Odoo’s first setup in Greece. If you’re moving to Odoo from other software, see how moving to Odoo works without stopping the business.