Keep your ERP now, and move to Odoo later, step by step.

Many people think of it this way: since something has to change by January, let’s change the software too. It sounds sensible, but in practice it loads two big changes into the same three months.

Changing ERP takes mapping, cleaning up the data, setup, testing and training. A first phase with sales, inventory and invoicing in Odoo usually takes six to eight weeks. And right now it lands on December, the busiest month for most trading companies, and on the year-end stock count.

The more serious problem is something else. If an invoice doesn’t go out in the first week of February, you won’t know whether the new software, the connection to the provider or the data you moved over is to blame. With one change at a time, you find it straight away.

Only one thing is mandatory: from 1 February 2027, the invoices you issue from your software must go out through a licensed provider. Your software stays the same, and your team keeps issuing invoices as it does today. The provider signs them and sends them to myDATA, and the MARK (the number AADE, the Greek tax authority, gives the invoice) comes back to the software with the QR code.

First ask the company behind your software whether it has a ready-made connection to a provider, with which providers and from when. If your Greek company invoices from your group’s ERP, ask whoever supports it for the group. If there is no connection, or it doesn’t cover you, the software connects to the provider through eInvoice Link, as long as it has an API or we can read its database. You don’t need to replace it.

Check the start declaration with your accountant too. The transition period up to 31 January 2027 applies to those who filed the declaration that they issue documents electronically (Δήλωση Έναρξης Ηλεκτρονικής Έκδοσης Στοιχείων) in time, with a start date up to 2 November 2026. If anything is missing, talk to your accountant straight away.

You’ll find every date, the penalties and a checklist in the guide to Greek e-invoicing from 1 February 2027. Don’t count on an extension: the connection takes a few weeks, and January will be busy for everyone.

No, if you arrange it from the start. The provider isn’t part of your software. When you move to Odoo, you keep the same provider and the same subscription with them, and only the software that sends them the invoices changes.

If the connection goes through eInvoice Link, the change is simpler still. First the software you use today sends invoices to it, later Odoo does, and eInvoice Link forwards them to the same provider. On the day invoicing moves to Odoo, the provider sees no difference.

If instead your software connects through its own ready-made connection, ask now whether the provider you choose also connects to Odoo. That way you won’t have to change provider later. What else to ask before you sign is in the guide to choosing an e-invoicing provider.

Digital delivery notes move to Phase B1 from 1 January 2027, a month before invoicing. From then on, loading, transhipment and receipt, with a check of quantities, are also recorded in myDATA, and this usually touches the same software.

The same logic applies here. Ask whether the software you use today supports Phase B1, and don’t change software for it in December. When the warehouse moves to Odoo, in step 2 below, delivery notes will be issued from there. What changes in practice is in the guide to delivery notes, Phase B.

After February, without the pressure of the deadline, you move to Odoo one piece at a time. Invoices keep coming from the software you use today until you’re ready. How the switch itself works, with trial migrations and checked balances: moving to Odoo.

While orders are in Odoo and invoices still in your ERP, every order has to reach the ERP for the invoice to be issued. How that happens, and which system has the last word on stock, we write down beforehand in the connection map. That’s why we keep this in-between period as short as we can.

We test every step first in a test environment, not in the system you work in, and a step starts only when the previous one runs without surprises.

Three reasons make the eshop and the warehouse the best first step:

• You see the benefit from the first week. Eshop orders go into Odoo by themselves, without being typed twice, and the stock on the eshop and the marketplaces is what’s on the shelf. See how we set up eshop–ERP integration.
• Invoices stay as they are. Your accountant works as before, and the connection to the provider you set up in January doesn’t change.
• Your team learns Odoo in its daily work, on something that, if it goes wrong, never reaches AADE.

When your team is at ease in Odoo and your accountant has seen test invoices from it. Choose a clean date together, for example the start of a VAT period, so that each period’s invoices come from one system only.

Before the switch, we test every type of document you issue: invoices, credit notes, and invoices to the public sector if you have any. The add-ons of the Greek suite for Odoo make sure every document gets the right myDATA type. On the day of the switch, the old software stops issuing invoices and Odoo starts. You keep the old one to look up past documents for as long as you need it.

For some companies, changing now does make sense: those that have already started moving to Odoo, or those whose software can’t be connected to a provider in any way. If you’re not sure where you belong, the readiness check tells you in two minutes what your case needs.

1. Find out whether your software sends straight to myDATA today. If it does, that stops on 31 January 2027.
2. Ask the company behind your software whether it has a ready-made connection to a provider, with which providers and from when.
3. Choose a provider from AADE’s list that also connects to Odoo, directly or through eInvoice Link.
4. Check with your accountant the start declaration and the provider’s authorisation in Taxisnet, the tax authority’s online portal.
5. Test before January: invoices, credit notes, the MARK and QR code back in the software, and what happens if the connection drops.
6. Set a date for the first step in Odoo after February: eshop, orders and stock. See how we set up Odoo for companies in Greece.