APIs and integrations

Which APIs are needed for e-invoice?

⚠ Machine-translated answer, not yet manually reviewed. For the exact wording, see the Slovak original.

Short answer

The law does not require a particular API. A business issuing only a few invoices may use a provider portal or invoicing application without any API integration. ERP systems, e-shops and automated workflows commonly use APIs to create and validate e-invoice, submit it through a delivery-service provider, receive delivery statuses and exchange data between systems.

When do you not need an API at all?

You generally do not need an API if:

  • you issue invoices manually,
  • you use a e-invoicing delivery-service provider’s web application,
  • you issue only a small number of invoices,
  • you do not integrate e-invoices with other systems.

In such cases, the provider’s user interface is sufficient.

When do you need an API?

An API is particularly useful when you want to automate tasks or integrate multiple information systems.

Typical examples include:

  • ERP systems,
  • accounting software,
  • invoicing applications,
  • online shops,
  • warehouse management systems,
  • CRM systems,
  • custom business applications.

Which APIs are most commonly used?

API for creating e-invoices

Allows you to generate an XML e-invoice from data in your system.

Validation API

Verifies whether the e-invoice complies with XML technical rules, the EN 16931 standard, Peppol BIS Billing and any relevant Slovak specifications.

API for sending e-invoices

Used to submit a valid e-invoice to a e-invoicing delivery-service provider, which will ensure its delivery.

API for receiving e-invoices

Enables your system to retrieve received e-invoices from the digital post office without the need for manual downloading.

Status tracking API

Using webhooks or regular status checks, the ERP system can obtain information on whether an e-invoice has been received, delivered, rejected or whether an error occurred during processing.

Import and export API

Used for exchanging data between the ERP, accounting, warehouse, e-shop and archive.

Do I need all these APIs?

No. The APIs required depend on how the business operates. A small business may manage without any APIs, whilst a larger company may use several interfaces simultaneously.

What does the law not require?

The VAT Act does not specify what type of API you should use, what technology you should use, or even whether you are required to use an API at all. The legislation sets out requirements for electronic invoices and their delivery, not for the internal architecture of information systems.

Most common mistakes

  • “I need an API from the Financial Administration for e-invoices.” No. Electronic invoicing does not require every business to be directly connected to the Slovak Financial Administration’s API.
  • “I can’t issue e-invoices without an API.” No. Small businesses can use a web interface or the features of their invoicing software.
  • “One API solves everything.” No. In practice, individual functions are usually split across several separate interfaces.

Conclusion

Which API you’ll need depends on how your business operates. For small businesses, a digital mail service’s web application or an invoicing programme without any programming integration is often sufficient. Companies wishing to integrate electronic invoicing into their ERP, e-shop or proprietary information systems most commonly use APIs to create, validate, send, receive and track the status of e-invoices. However, the law itself does not require the use of a specific API.

This is not legal advice. Sources: Act No. 222/2004 Coll. on VAT, EN 16931, Peppol BIS Billing 3.0 and publicly available documentation on e-invoices. Verified on 10 July 2026.

Related questions

Review of questions from an earlier presentation

The presentation by the Slovak Accountants’ Centre was used solely to identify practical issues. The following conclusion has been updated in line with a subsequent FAQ from the Financial Administration and the applicable legislation; we do not treat the author’s suggestions, recommendations or incorrectly merged fragments as legal rules.

  • slide/page 38: What if I only need to receive electronic invoices?
  • slide/page 38: What does receiving electronic invoices via a web mailbox mean?

Current conclusion: The law does not prescribe a specific API. An entity that only needs to receive invoices may use the post office’s web or mobile application; an API is only required depending on the extent of automation and integration with an ERP system or accounting software.

Primary sources: FAQ Financial Administration of the Slovak Republic k e-invoice, July 2026; Act No. 222/2004 Coll. on VAT Effective from 1. 1. 2027. Revised 13 July 2026.