Data box for self-employed people: duty since 2023 and changes for 2026

You get a data box whether you want one or not

Since 1 January 2023, the rule has been simple: if you have an IČO (business identification number), you have a data box (datová schránka). The state creates it automatically and free of charge by law for every entrepreneurial natural person, without exception. It does not matter whether you earn millions or only take weekend photography jobs on the side. It also applies to entrepreneurs with suspended activity.

Previously, few people set up a data box voluntarily. The change came with an amendment to Act No. 300/2008 Coll. From 2023, a data box is a duty for self-employed people, not a choice.

Say you set up an unrestricted trade in March. As soon as the Trade Licensing Office assigns IČO and enters you in the register, the box-creation process starts in the background. You do not file any separate application.

What a data box is actually for

A data box is the electronic equivalent of registered mail. It is a secure channel for communication with authorities and has several practical functions:

• Receiving official messages - the tax office, ČSSZ, Trade Licensing Office, court or enforcement officer deliver decisions, requests and notices here.
• Sending filings to authorities - from the data box you can send a document to an authority with the same validity as a filing with a verified signature.
• Communication between companies and persons - a so-called postal data message, a paid service that a new self-employed person usually need not deal with.

The big advantage: messages arrive immediately and official communication is free. No post-office queues and no collection slips. The big disadvantage: you must watch the box. That brings us to the most important part.

Watch deemed delivery: 10 days that can cost you a lot

Read this twice. Deemed delivery means that if you do not log in to the box, a message is deemed delivered on the tenth day after it was delivered to the box (Section 17(4) of Act No. 300/2008 Coll.). This applies even if you never opened it and did not know about it.

The consequence? From deemed delivery, deadlines start to run: the deadline for an appeal, payment or response to a Tax Administration request. If you miss it because you did not check the box for three weeks, the authority will not care. From its perspective, delivery was proper.

Model situation: the tax office sends you a request on 2 April to supplement your tax return with a 15-day deadline. You are on holiday and do not log in. On 12 April, deemed delivery occurs. The deadline expires in mid-April; you log in only on 1 May and it is too late.

How to protect yourself:

1. Turn on notifications. In the data-box settings at mojedatovaschranka.cz, set an e-mail alert (free) or SMS alert (paid).
2. Check the box regularly. Ideally make it a routine, for example every Monday. Ten days pass quickly.
3. Remember it during suspension too. The box remains active and deemed delivery continues.

Warning: Notifications are only a helper. Even if the e-mail does not arrive because of spam or a changed address, deemed delivery still occurs. Responsibility for checking the box is always yours.

How to log in for the first time

After the box is created, the state sends you access details. They are delivered either by post as a registered item delivered personally only to the addressee, or to your existing personal data box if you already have one.

With the login name and password, log in at www.mojedatovaschranka.cz. On first login you will be asked to change the password. You do not have to use only this method; login through Citizen Identity works as well, for example with bank identity, eObčanka or the Mobile Key of eGovernment.

Key date: activation on the 15th day. If you do not log in yourself, the box is automatically activated on the 15th day after delivery of the access details. From activation, all consequences apply, including delivery and deemed delivery. In other words, even if you put the access details in a drawer, the box starts working by itself.

Practical tip: after first login, set notifications and connect the box with an app such as Mobile Key of eGovernment or Datovka. If an accountant or tax adviser handles business matters for you, you can give them their own access in Settings -> Users.

A data box changes how you file returns and statements

This is the consequence many new self-employed people discover only later. An established data box changes the mandatory form of your filings.

Tax return to the Tax Administration

If a self-employed person has an accessible data box created by law, form filings to the Tax Administration must be made exclusively electronically as a data message in the prescribed format and structure (Section 72 of the Tax Code). Paper forms handed in at the counter are over.

In practice, you can file electronically through MOJE daně with data-box or Citizen Identity login, or by sending an XML file to the tax office's data box.

Warning: Failure to keep the electronic form where required by law can lead to a fine of up to 50,000 Kč (Section 247a of the Tax Code, Act No. 280/2009 Coll.). Filing on paper when you have a data box is therefore not worth it.

Statements for ČSSZ and the health insurance company

The income and expenses statement for self-employed people for the social security administration is also filed exclusively electronically, including through a data box or the ČSSZ ePortal. From 1 January 2026, the same electronic-filing duty also applies to the health-insurer statement, which could previously be submitted on paper. The data box is the natural tool for this: one login handles electronic filing for the tax office and both insurers.

Data box during suspension and cancellation of a trade

A common question is: "If I stop doing business, does the box disappear too?" The answer is not entirely straightforward.

Important: a data box of an entrepreneurial natural person cannot be cancelled while the trade exists. The only way to get rid of it is to end the business activity. After deletion from the Trade Register, the Ministry of the Interior disables it, usually after the statutory period under Act No. 300/2008 Coll.; verify the exact period with the Ministry of the Interior.

And again the most important reminder: during suspension of the trade, the box continues to work. Many people think that when they "put the trade to sleep", official delivery stops. It does not. Deemed delivery applies during suspension too, so watch the box just as carefully.

Summary: five things to remember

• You have the box automatically from 2023 if you have IČO, without exception, even for secondary activity.
• Access details arrive by post into your own hands; if you do not log in, the box activates itself on the 15th day. You can also log in through Citizen Identity.
• Deemed delivery after 10 days is the biggest risk: enable notifications and check the box regularly.
• Returns and statements (from 2026 also for the health insurance company) must be filed electronically because of the box, otherwise a fine of up to 50,000 Kč may apply.
• You cannot cancel it while the trade exists; during suspension it remains active.

A data box is not an enemy. Once you get used to it and set alerts, it saves trips to the post office and authorities and lets you handle everything from home. Just do not underestimate it.

Want the exact step-by-step process and current statement deadlines for 2025 filed in 2026? Read the detailed guide to data boxes for self-employed people, with a deadlines table and instructions for notifications and accountant access.