Electronic invoicing is nothing new. In parts of the business world, it has been standard practice for decades — for example in retail chains, the automotive industry, and other sectors. The real challenge is the accessibility of this service (cost, technical integration) and the large number of different formats involved. For a small or medium-sized company, implementing electronic invoicing can be quite expensive. But with Odoo, it is very simple:

• Register in the PEPPOL network.

• Send and receive invoices electronically.

And that is all.

Really? Well, not quite — there is a bit of technical magic , legislation, and more behind it, so let’s take a closer look.

Registration

First of all, a participant must be registered in the PEPPOL network. You can find the registration in the Accounting settings. To register, you need to fill in the correct company details, a contact email, and a phone number. At the moment, Slovak companies can register using their VAT ID (SK123456789), but registration via Tax ID will soon also be available.

After verification, Odoo (which is a certified PEPPOL access point — also called an “access point” or a “digital postman”) registers you in the central directory, which is similar to a phone book , where other participants — in other words, other companies — can find you.

Sending an invoice

Alright, we are successfully registered — but what about our customer? How do I know whether they are registered in the PEPPOL network or not?

Simple. As soon as you enter your customer’s VAT ID into Odoo, Odoo checks whether they are part of the PEPPOL network. And since Odoo knows it, you know it too — that is what an information system is for, after all.

And what about all those formats we mentioned at the beginning? That has also been taken into account. During registration, Odoo records which electronic invoice formats we can process. Odoo also checks the same information for your customer.

So Odoo knows whether your customer is in the PEPPOL network and which format they can receive invoices in. All that is left is to press the “Send” button. Odoo automatically sets the option to “via PEPPOL,” and off it goes. Odoo creates an XML file with your invoice data, including the PDF document, and hands the invoice file over to the digital postman (Belgian Odoo s.a. as a company), and moments later it is flying .

Receiving invoice

Odoo regularly checks for and downloads incoming invoices (yes, including credit notes and debit notes). It downloads them, stores them in Documents, or directly creates a vendor bill. All that remains for you is to review, approve, and post it.

Come on, how much is it going to cost?

Fair question and we are happy to admit it. Sending and receiving invoices in Odoo costs you nothing extra. Don’t believe it? Too bad, it is true. Nothing extra beyond the user price. In other words, sending and receiving invoices is already included. Nice little gift, isn’t it? 

And what do I actually gain from it?

Quite a lot. (Of course, we are an IT company, so hopefully nobody expects us to be against digitalization.)

• Cheaper than regular mail
  (And if you still want to support the postal service, you can continue sending invoices by post — but please think of our forests.)

• Cheaper than specialized EDI systems
  (Standards and large volumes bring costs down.)

• Faster booking of incoming invoices
  (Your accountant is qualified for accounting, not for retyping received invoices.)

• Safer than sending invoices by email
  (Fraudsters will not be rushing to voluntarily join e-invoicing.)

I will not believe it until I see it

That is why we have prepared an open test for you. Simply write to efaktura@26house.com and we will set up access to Odoo for you.

Everything is ready, so you can conveniently test sending invoices between companies connected to the PEPPOL test network. Everything works just like in live operation (sending, participant verification, receiving, and more). And if your accounting or ERP system is connected to PEPPOL Test, you can send an invoice or credit note to us — or we can send one to you .

What if...?

What if the customer does not have a system as good as Odoo and the invoice does not load properly?

Odoo can send the invoice both by email and via PEPPOL, so simply send it both ways.

How can I be sure the customer received the invoice?

The PEPPOL network — more precisely, the customer’s access point — sends back a confirmation that the invoice was delivered, and Odoo will let you know. If something fails, Odoo will also tell you.

What we cannot guarantee is that the customer actually read the invoice or did not throw it away . But surely you do not have clients like that, right?

And who guarantees that the digital postman will not read the invoices?

Honestly? Only agreements and rules. It is the same as postal secrecy — the rules (the law) are set, but nobody can guarantee with absolute certainty that no one will ever read your letter. In the PEPPOL network, it is similar to sending an invoice by post, by email, or through another EDI system — it is always about trust between the sender and the (digital) postman.

Not just anyone can become a digital postman — they must go through certification. Technically, all communication in the network is encrypted, and no unauthorized person can enter it — not even you. Compared to letters or email, this is a major step forward in terms of security.

Likewise, Odoo’s digital postman does not store invoices. Stored invoices take up space, and storage costs money. And millions of invoices per month would take up a lot of space — and cost a lot of money.

What if my internet goes down?

In that case, Odoo will not work either, so you will not be able to create, send, or receive an invoice. And if it lasts a while, we invite you for a cup of coffee at our office at Jarošova 1 in Bratislava.

Slovak eInvoice

And what does this have to do with Slovak e-invoicing and digital reporting?

Once the Odoo access point is certified by the Slovak national authority, it will report the legally required data to the state. This way, you will simply fulfill your legal reporting obligation.

Oh, here it is — government spying.

Well, to be honest, the state wants VAT data — and naturally it wants it as quickly and as automatically as possible. Slovakia is not the first country in the world to introduce mandatory e-invoicing, and neither is the European Union. Many countries have been ahead of us for years (for example Australia, Brazil, Mexico, Singapore, India, Egypt, and others).

And logically, the state likes to digitalize the areas where it spends or collects* the most money.

* Cross out whichever does not apply 

…and do we really have to?

In short, electronic invoicing becomes mandatory in Slovakia from 1 January 2027, but until 2030 you may still agree with your customer on another delivery method outside a certified digital postman.

The electronic invoice format must comply with the EN 16931 standard (FacturX, NLCIUS, BIS 3 Invoice, and others), though in practice BIS 3 Invoice (and related formats) is what is being implemented in Slovakia.

So once again, it is the EU’s fault

Yes and no.

The EU also wants to digitalize VAT information in cross-border trade, but national reporting and e-invoicing remain in the hands of each member state.

Slovakia has chosen an already existing technical solution for how this will work in foreign trade: an existing electronic invoice standard (BIS 3), an existing delivery method (via the PEPPOL network), and the same reporting approach (the European standard for the Tax Data Document).

As IT people and as citizens, we are happy to see that the Ministry of Finance and the Financial Administration are not reinventing the wheel .