E-invoicing from 2027: what's changing and how to prepare

In short

• From January 1, 2027, e-invoicing in Slovakia is mandatory for all VAT payers in domestic business-to-business transactions
• An invoice can no longer be a PDF or paper — it must be a structured XML file compliant with the European standard EN 16931
• E-invoices are delivered via the Peppol network, and the tax authority receives their data at the same time
• A wider range of businesses must receive e-invoices than issue them, including some non-VAT payers
• Invoices to consumers (B2C) are not affected; cross-border transactions within the EU will be added from July 1, 2030

In three months, the way businesses in Slovakia invoice is changing. From January 1, 2027, VAT payers must issue invoices to other businesses as electronic invoices in a precisely defined format and send them via the international Peppol network. The obligation is introduced by Act No. 385/2025 Coll., which amended the VAT Act.

For businesses that invoice in a standard invoicing program, an update will usually take care of it. The problem is for those invoicing from their own system, an older ERP, an e-shop or custom software. There, e-invoicing has to be developed — and that takes time.

In this article, we explain exactly what's changing, who it affects and how to prepare so you aren't left unable to invoice in January.

What an e-invoice is and how it differs from a PDF

Many people think of an e-invoice as a PDF invoice sent by email. But from 2027, that's no longer enough for domestic business-to-business transactions.

Under the law, an e-invoice is a structured data file in XML format compliant with the European standard EN 16931 (in UBL 2.1 or CII syntax). It's not a document to read, but data: every item — supplier, customer, line items, prices, VAT, due date — has its exact place. The customer's system reads the invoice on its own, with no retyping.

A PDF, a scan or a Word document does not meet this requirement, even if they look the same.

Who mandatory e-invoicing applies to

Issuing

E-invoices must be issued by VAT payers established in Slovakia — limited liability companies, joint-stock companies, sole traders and non-profits registered for VAT. The obligation covers domestic invoices to businesses and entrepreneurs (B2B) and to the public sector (B2G).

Receiving

The obligation to receive e-invoices is broader. It applies to businesses and entrepreneurs, including some entities that aren't VAT payers. If you receive invoices from suppliers, you must be able to receive them in electronic form too.

Who it doesn't apply to

• Invoices to consumers (B2C) — regular invoices to private individuals, for example from an e-shop, stay as they are today.
• Most cross-border transactions — under the European ViDA package (VAT in the Digital Age), these will be added from July 1, 2030.

How an e-invoice travels: Peppol and the digital postman

Slovakia chose the so-called five-corner model built on the Peppol network. It's an international network for the secure exchange of electronic documents between businesses, used for years by countries such as the Nordics and Belgium.

In simple terms, it works like this:

1. Your system creates an XML e-invoice.
2. It sends the invoice to your digital postman — a certified provider, i.e. an access point to the Peppol network.
3. Your postman delivers it to the customer's postman.
4. The customer's postman passes it into the customer's system.
5. At the same time, the invoice data required by law is reported to the tax authority.

What matters most for you is that you no longer send the invoice by email — it leaves directly from your system. And your system has to be ready for that.

What this means in practice

You invoice in a standard invoicing program

Most well-known invoicing and accounting programs in Slovakia will add e-invoicing by the deadline. Check with your provider when and under what terms — and review your customers' details.

You invoice from your own system, ERP or e-shop

This is where most of the work is. If invoices are created in a custom system, an older ERP or an e-shop that invoices businesses, you need to add:

• generation of XML e-invoices with all mandatory data,
• a connection to a digital postman via API,
• delivery status tracking for every invoice,
• receiving e-invoices from suppliers.

You don't need to replace your whole system for this. Your current software can be connected to e-invoicing via API, so your team keeps working in an environment it knows.

You receive a lot of invoices

E-invoicing is also an opportunity. Because a received invoice contains structured data, it can be read automatically, matched with an order or delivery note and sent for approval. No more retyping or hunting for invoices in your inbox.

How to prepare: a checklist

1. Find out where you invoice from. List every system that produces invoices — invoicing program, e-shop, ERP, booking or ordering system.
2. Check that each one is ready. For off-the-shelf programs, ask the vendor; for custom systems, ask the developer.
3. Clean up customer data. Correct company ID, tax ID and Peppol ID determine whether an invoice arrives. Incorrect data is the most common reason for an undelivered e-invoice.
4. Choose a digital postman. Or a partner who handles the integration for you.
5. Prepare for receiving too. Agree with your accountant how received e-invoices will flow into accounting and who approves them.
6. Test on real invoices. Before January, try out advance invoices, credit notes and invoices with multiple VAT rates.
7. Train your team. Who issues invoices, who checks delivery status and what to do when a customer rejects an invoice.

Why not wait until December

Programming the integration itself doesn't have to take long. The time goes into everything around it: finding out everywhere invoices come from, cleaning up the customer directory, testing exceptions and training people. If everyone shows up at once in December, they'll have to wait.

One more thing: e-invoicing isn't just an obligation. Businesses that implement it properly get rid of retyping received invoices, manually matching payments and searching for documents. With dozens of invoices a month, that's a noticeable time saving.

How we help with e-invoicing

We build business systems ourselves on the Laravel and Symfony frameworks, so we can add e-invoicing directly to your system:

• connecting your existing ERP, e-shop or CRM to send and receive e-invoices via Peppol,
• automatic processing of received invoices — reading, matching with orders, approval and export to accounting,
• e-invoicing in our CRM and ERP Proon, if you're looking for a new system with quotes, inventory and invoicing in one place,
• custom invoicing modules and applications for businesses with their own invoicing rules,
• white-label e-invoicing for software companies that want to offer it to their customers.

Learn more on our e-invoicing and Peppol integration page.

Frequently asked questions

When does e-invoicing become mandatory in Slovakia?

From January 1, 2027, for domestic invoices between businesses and invoices to the public sector. Cross-border transactions within the EU will be added from July 1, 2030.

Do I have to issue e-invoices if I'm not a VAT payer?

E-invoices must be issued by VAT payers. However, a wider range of businesses, including some non-VAT payers, must be able to receive them.

Is it enough to send a PDF invoice by email?

Not for domestic business-to-business invoices from 2027. An e-invoice must be a structured XML file compliant with EN 16931. A PDF, a scan or a Word document does not meet this requirement.

Does e-invoicing apply to e-shops?

Only to invoices for businesses. Invoices to consumers (B2C) aren't subject to the e-invoicing obligation. If an e-shop also sells to businesses, it must issue them e-invoices from 2027.

What is a digital postman?

A certified provider, an access point to the Peppol network. It delivers your e-invoice to the customer's postman and at the same time reports the data required by law to the tax authority.

Do I have to change my invoicing system because of e-invoicing?

Usually not. Off-the-shelf programs will get an update, and custom systems can be connected to e-invoicing via API. Replacing the system only makes sense if it can't handle the new requirements or you're planning to replace it anyway.

Current as of October 3, 2026. This article is based on Act No. 385/2025 Coll.; for details on mandatory data and deadlines, follow the website of the Financial Administration of the Slovak Republic. This article is not tax advice.
Authors: the MR. Digital team