Slovak e-invoicing 2027: PDFs will no longer be valid invoices. Structured data will be what counts

A PDF invoice arrives by email and is then saved or manually entered into an accounting system. This common practice will change with the introduction of mandatory e-invoicing in Slovakia in 2027. PDFs will no longer meet the requirements for an electronic invoice. Instead, the standard will be a structured electronic document whose data can be automatically read and processed by information systems. However, this does not mean that accountants will have to work with XML files instead of invoices.

As of January 1, 2027, mandatory electronic invoicing for legally defined domestic B2B and B2G transactions will be introduced in Slovakia. Invoices will be exchanged via certified digital postmen and the Peppol network. The significant change, however, is not just in the method of delivery; the very format of the e-invoice is changing as well.

An electronic invoice will be a structured data document that complies with established rules. The Slovak system is based on the European standard EN 16931 and uses the Peppol BIS Billing 3.0 format. A standard PDF sent electronically does not meet these requirements.

PDF is for humans, structured data is for systems

At first glance, both invoices may look the same. They contain the supplier and customer details, line items, amounts, due dates, and other information necessary for accounting. The difference lies in how this information is stored and how information systems can work with it.

PDFs are created primarily for human readability. Therefore, an accounting system usually needs to extract the necessary data first—either through manual entry, data extraction software, or other methods.

In a structured e-invoice, each piece of data has a precisely defined format and meaning. The recipient's system knows exactly which value represents the invoice number, the supplier's tax ID, the amount, the VAT rate, or the due date. It can ingest the data directly and proceed with further processing.

Structured data will be the foundation of the Slovak e-invoice starting in 2027. PDFs do not have to disappear from companies entirely. They can still serve as a visual representation of the document for accountants to open, read, or use for internal checks. However, from the perspective of mandatory e-invoicing, the structured electronic document will be the decisive factor, not its PDF preview.

Accountants don't need to work with XML

The term "structured invoice" might give the impression that the daily work of accountants will change significantly. In reality, there is no reason for a user to open an XML file or check its technical structure.

Smaller companies and sole traders can create and receive e-invoices directly within a digital postman application. They work in a standard user interface, and the necessary data structure is generated in the background.

Medium and large companies can continue to issue invoices from their ERP or accounting system. The digital postman will take the billing data, validate it, convert it to the required format if necessary, and handle the subsequent communication. It can deliver received e-invoices into the company's processing system in the same way. There is no need to change a functional ERP system just because the format and method of invoice exchange are changing.  

This is exactly what companies should focus on when preparing for Slovak e-invoicing. It is not enough to verify that they can display an invoice as a PDF. They need to know where the data for a structured e-invoice comes from, who verifies its accuracy, and how the document reaches the recipient or, conversely, enters their accounting process. For companies with a higher volume of documents, integration with existing ERPs, EDI communication, and other systems is also essential so that the new regime does not result in extra manual work.

As a certified digital postman, GRiT handles the receipt of billing data, its verification and preparation into the required structure, secure delivery, and the transfer of information back into company systems. Smaller firms can use a standalone application, while larger companies can integrate e-invoicing into their current environment.

Would you like to see in advance how issuing and receiving Slovak e-invoices will work? Try our free e-invoicing demo from GRiT.