How does the tax office deliver documents?

The main method is through the data box system (datová schránka), which is mandatory for companies and often used voluntarily by individuals. A document is considered delivered:

• on the day you log in and open it,

• or automatically on the 10th day after it was sent—even if you never read it (this is called fictional delivery).

Another option is standard mail—registered letters that must be collected in person. If you don’t pick it up, the document is considered delivered after a certain time. This rule applies even if you were on vacation, sick, or “just missed it.”

What does this mean in practice?

Deadlines begin from the day of delivery, not the day you actually read the document. So if you have 15 days to respond, but open the letter three weeks later, your deadline has already passed. The tax office is not required to give you another chance—and usually won’t.

This also affects your right to appeal. If a decision was delivered and you didn’t respond within the appeal period, you may lose the right to challenge it.

How to avoid this risk?

• Check your data box regularly, or set up email notifications.

• Authorize someone you trust to access it if you’ll be away or unavailable.

• Don’t ignore missed letters—even unopened ones can have legal effects.

In my legal practice, I’ve seen many cases where people got into serious trouble just because they missed one envelope. And yet, the solution is usually simple: timely checks and asking for help when needed.