What must an electronic invoice contain?

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Between 1 January 2027 and 30 June 2030, mandatory electronic invoicing for VAT payers will be introduced into the Slovak legal system, together with the obligation to electronically report data on the supply of goods and services. In this article, we will explain what every invoice issued in accordance with the law must contain and what requirements an electronic invoice must meet. You will also find out whether it is necessary to attach an electronic signature to an electronic invoice.

Mandatory elements of an invoice and an electronic invoice

Act No. 222/2004 Coll. on Value Added Tax (hereinafter referred to as the “VAT Act”) defines both an invoice and an electronic invoice in Section 71 and the following provisions.

Invoice: According to this legal regulation, an invoice is any document or notice issued in paper or electronic form in accordance with this Act or in accordance with the legislation of another EU Member State governing the issuance of invoices.

Electronic invoice: An electronic invoice is an invoice that contains the information required under Section 74 of the VAT Act and is issued and received in any electronic format. An electronic invoice may only be issued with the consent of the recipient of the goods or services.

The law also considers any document or notice that amends the original invoice and clearly refers to it as an invoice. An electronic invoice must contain the same information as a standard paper invoice.

An invoice (including an electronic invoice) must contain the following information:

• Supplier identification details:
  The name and surname of the taxable person or the business name of the taxable person, the address of their registered office, place of business, establishment, residence or habitual residence, and their VAT identification number under which the goods or services were supplied.
• Customer identification details:
  The name and surname of the recipient of the goods or services or the business name of the recipient, the address of their registered office, place of business, establishment, residence or habitual residence, and their VAT identification number under which the goods or services were supplied.
• Invoice numbering: A sequential invoice number.
• Date of supply of goods or services: The date when the goods or services were supplied or the date the payment was received if this date is known and differs from the invoice issue date.
• Invoice issue date: The date when the invoice was issued.
• Information about goods or services: The quantity and type of goods supplied or the scope and type of services provided.
• Tax information: The tax base for each tax rate, the unit price excluding VAT, and any discounts or rebates if they are not included in the unit price.
• Payment information: The total amount to be paid.
• Other information: Additional information and details required under Section 74 of the VAT Act.

An electronic invoice may take the form of a structured message, for example in XML format, or it may be issued as a PDF document. The law does not prescribe a specific electronic invoice format. The choice of format is up to the entrepreneur. The important requirement is that the invoice is created in an electronic format.

Warning:
An invoice that was originally issued in paper form and later scanned and attached to an email is not considered an electronic invoice under the law.

Signing and securing an electronic invoice

The law does not require entrepreneurs to sign an electronic invoice with an electronic signature. However, a qualified electronic signature is one of the relevant ways to secure an electronic invoice in accordance with the law.

When issuing an electronic invoice, the VAT Act requires you to ensure:

• Authenticity of origin: Authenticity of origin means confirmation of the identity of the supplier of the goods or services, or the person who issued the invoice on behalf of the supplier.
• Integrity of content: Integrity of content means that the invoice content remains unchanged and protected from unauthorized modifications.
• Readability: The electronic invoice must remain readable throughout the entire retention period.

Methods of securing an invoice

• Internal business processes: These include control mechanisms within company processes that reliably ensure the link between the invoice and the documents related to the supply of goods or services.
• Qualified electronic signature: An advanced or qualified electronic signature under a specific legal regulation or according to the legislation of another EU Member State regulating the use of electronic signatures.
• Electronic data interchange (EDI): Used when a contract governing such exchange establishes procedures ensuring authenticity of origin and integrity of the data.
• Other security methods: Any other method that ensures authenticity of origin and integrity of the invoice content.

Tip:
Some entrepreneurs still use stamps on invoices. However, there is no legal requirement to place a stamp on an invoice. It is entirely optional.

Electronic signature from the NFQES platform

As mentioned at the beginning of this article, the amendment to the VAT Act introduces mandatory electronic invoicing for VAT payers effective from 1 January 2027. At the same time, until 30 June 2030, it establishes the obligation to issue and receive invoices in a specified electronic format.

In the future, the obligation to issue electronic invoices will apply to domestic transactions and will concern all taxable persons for whom VAT payers are required to issue invoices. This obligation represents the transposition of Articles 1 and 5 of Council Directive (EU) 2025/516 of 11 March 2025, which amends Directive 2006/112/EC.

However, a growing number of business activities and communication are already rapidly moving into the online environment, and entrepreneurs are increasingly required to communicate with public authorities exclusively electronically. For many entrepreneurs, purchasing a qualified electronic signature with the highest legal validity is therefore a logical step.

A qualified electronic signature ensures the authenticity of signed documents, their integrity, and non-repudiation in electronic communication. This makes it possible to clearly verify the identity of the signing party and prove that the signed document has not been altered.

A qualified electronic signature can be issued quickly and easily by the certification authority BRAIN:IT, which operates the NFQES digital platform. In addition to saving time, using an electronic signature also brings several financial benefits. Find out where you can save costs by using an electronic signature.