Data box for businesses in Czechia 2026: obligations and deadlines

A data box is a reality Czech entrepreneurs can hardly avoid today. Most companies and sole traders have one, but many are unaware of the obligations that come with it — and those are exactly what decide whether they miss an important deadline.

It is not just another email inbox. Delivery into it has legal effects and it carries an obligation of electronic submissions. Let's go through who has one, what deemed delivery means and what you must file through it.

What a data box is and who has one

A data box is a secure electronic store through which delivery between the authorities and a subject takes place. It is set up by the Ministry of the Interior, and since 1 January 2023 every legal person (including an s.r.o.) and every self-employed person (a sole trader) gets one automatically by law. Non-business individuals can have one too, for example on the basis of a bank identity.

For an entrepreneur this means you almost certainly have a box set up, even if you never applied for one. Official post arrives in it from the tax office, the social security administration, the health insurer, the courts and the trade licensing office — communication you cannot afford to overlook.

Deemed delivery — the most important deadline

The most important rule of the whole box is deemed delivery. A message is considered delivered the moment you log into the box — but at the latest after ten days from when it was placed there, even if you never read it. From that moment, deadlines start to run.

Example: if a decision of the tax office with a deadline to respond arrives in your box, the deadline runs from (deemed) delivery — not from the moment you actually open the message. That is precisely why you must check the box regularly, and it is well worth turning on email or SMS notifications so no message slips past you.

Mandatory electronic submissions

The box also comes with an obligation to file certain things electronically. Anyone who has a box set up by law must file form-based submissions — typically the tax return — electronically; a paper submission no longer holds up and carries a penalty. The deadlines are covered in the article tax returns.

This trend continues in 2026 — sole traders' overviews for the social security administration and the health insurer are also filed electronically. Communication with the authorities is thus moving online and paper is in retreat; a broader overview of the changes is in the article legal changes for businesses 2026.

How to use the box in practice

You access the box through the Citizen Portal, through a mobile app or with a bank identity. First of all, turn on notifications — it is the simplest way to avoid deemed delivery without having to log in every day. If you are in business, it pays to grant access to your accountant too, so they see official post in time.

Think about archiving as well. Messages are automatically deleted from the box after a while, so download and store important documents on an ongoing basis. The box also allows so-called postal data messages — paid communication between companies — which can replace a registered letter, but you do not need it for ordinary dealings with the authorities.

Conclusion

Today every company and sole trader automatically has a data box, and two things are key: deemed delivery after ten days and mandatory electronic submissions. Regular checking and switched-on notifications are therefore a necessity, not a choice. How a trade licence, which triggers the box, is set up is covered in the article how to get a trade licence.

Frequently asked questions