Data Mailbox for OSVČ: obligations and how to use it

From 1 January 2023, all OSVČ are required to have a data mailbox. This change introduced a number of new obligations that many self-employed people still don't fully understand. A data mailbox isn't just another "digital obligation" — used properly, it can significantly simplify your communication with authorities and save you both time and money. In this article, you'll learn everything you need to know about data mailboxes as an OSVČ.

What is a data mailbox

A data mailbox is an electronic storage space set up by the state, used to deliver electronic documents between public authorities and individuals or legal entities. It works like official electronic mail, with state-guaranteed identities for both sender and recipient.

Key features of a data mailbox

• Legal validity — a message delivered to a data mailbox carries the same legal weight as a registered letter with acknowledgement of receipt
• Deemed delivery — if you don't log into your data mailbox within 10 days of a message being delivered, the message is considered delivered on the last day of that period
• Free of charge — communication with public authorities is free
• State-guaranteed identity — the recipient can be certain of who sent the message

History of mandatory data mailboxes for OSVČ

Data mailboxes have existed in the Czech Republic since 2009. Initially, they were only mandatory for legal entities registered in the Commercial Register and for public authorities. For OSVČ, they were voluntary.

The 2023 change

Act No. 261/2021 Coll. brought a fundamental change. From 1 January 2023, data mailboxes are automatically set up for all OSVČ. If you are an OSVČ and didn't previously have a data mailbox, one was created for you automatically and your login credentials were sent by post.

What this means in practice

• Your data mailbox was set up automatically — you didn't need to apply for it
• Your login credentials were sent by post to your permanent address
• If you didn't receive your credentials or have lost them, you can request new ones at a Czech POINT contact point

How to log into your data mailbox

Login methods

There are several ways to log into your data mailbox:

1. Username and password — the basic method
2. eIdentita — login using your electronic identity (NIA)
3. Bank identity — login via your bank (most convenient)
4. Certificate — for advanced users

Obligations arising from having a data mailbox

Having a data mailbox comes with several important obligations you need to be aware of.

1. Obligation to file tax returns electronically

From the moment your data mailbox is activated, you must file tax returns electronically. This applies to:

• Personal income tax returns
• VAT returns (if you are VAT-registered)
• Control statements (if you are VAT-registered)
• Summary statements
• Road tax
• And other tax declarations

2. Regular checking of your data mailbox

You must regularly check whether any new messages have arrived in your data mailbox. Remember deemed delivery — after 10 days, a message is considered delivered even if you haven't read it.

3. Electronic communication with authorities

If an authority has the option to send you a document via your data mailbox, it will do so. You will no longer receive letters by post (except in special cases).

Obligations that do NOT arise from having a data mailbox

• You are not required to communicate with private entities through your data mailbox
• You are not required to send invoices through it
• You are not required to submit reports to the Czech Social Security Administration (ČSSZ) and health insurance companies through it (but you can)

How to file tax returns electronically

There are two main methods of electronic filing:

1. Via the MY Taxes portal (EPO)

The Tax Administration portal offers electronic forms for all tax filings.

2. Sending directly from your data mailbox

You can also send a completed XML file directly from your data mailbox to the filing office of the relevant tax authority.

3. Via accounting software

Many accounting programs can generate filings in XML format and send them directly via your data mailbox or the EPO portal.

Setting up notifications — don't miss important messages

One of the most important steps after activating your data mailbox is setting up notifications.

Practical uses of your data mailbox

A data mailbox isn't just an obligation — it can genuinely make your life easier. Here are some practical ways to use it:

Communication with the tax authority

• Filing tax returns
• Responding to tax authority requests
• Applications for a tax overpayment refund
• Applications to defer a tax payment

Communication with ČSSZ and health insurance companies

• Submitting income and expenditure overviews
• Notifying changes (starting/ceasing activity)
• Applications to reduce advance payments

Communication with other authorities

• Trade licensing office
• Land registry
• Courts
• Municipalities and regions

Communication between private entities

Since 2010, it has been possible to send messages between private data mailboxes. However, this service is paid (approx. 5 Kč per message).

Archiving messages from your data mailbox

Messages in your data mailbox are only retained for 90 days. After this period, they are automatically deleted (unless you have the paid Data Vault service).

How to archive messages

Data mailbox security

Protecting your login credentials

• Never share your login credentials with unauthorised persons
• Use a strong password and change it regularly
• Consider logging in via bank identity (more secure than a password)
• Log out after every session

Authorising another person

If you want someone else — such as your accountant — to have access to your data mailbox, you can grant them authorisation:

• Authorised person — has access to messages, can read and send them
• Administrator — has full access including settings

You can set up authorisation in Settings > Authorised persons.

Common issues and how to resolve them

Lost login credentials

If you have lost your login credentials:

1. Visit a Czech POINT contact point (at any post office or municipal office)
2. Request that your login credentials be resent
3. Bring your ID card with you

Data mailbox is blocked

After three unsuccessful login attempts, your data mailbox is temporarily blocked. To unblock it:

• Visit a Czech POINT contact point
• Call the data mailbox helpline

I never received my login credentials

If you never received your login credentials:

1. Check whether they may have been delivered to a different address (the address in the trade register)
2. Visit Czech POINT and request that they be resent

I want to close my data mailbox

An OSVČ's data mailbox cannot be closed while you hold an active trade licence. The mailbox is automatically deactivated once you cease your business activity.

Data mailbox and the flat-rate tax regime

OSVČ in the flat-rate tax regime have simplified obligations — they don't need to file tax returns or income overviews. Nevertheless, their data mailbox remains active and deemed delivery applies to them as well. It is therefore essential to check your data mailbox regularly, as authorities may use it for any type of communication.

The future of data mailboxes

The digitalisation of public administration is ongoing and data mailboxes are playing an increasingly important role. In the coming years, we can expect:

• An expanded range of services available via data mailbox
• Better integration with the Citizen's Portal
• Possible connection with commercial accounting systems
• A simplified user interface

How DokladBot can help you with your data mailbox

Managing your data mailbox and keeping up with the associated obligations can be confusing. DokladBot can help you:

• Remind you of deadlines for filing tax returns and other forms
• Alert you to upcoming deadlines — so you never miss a time limit in your data mailbox
• Help you prepare the documents needed for electronic filings
• Answer questions about your data mailbox obligations
• Guide you through the process if you receive a request from the tax authority

With DokladBot, you'll always have a clear overview of your obligations and never miss an important deadline.

Try DokladBot — your AI accounting assistant at dokladbot.cz

Frequently asked questions (FAQ)

Do I need a data mailbox as an OSVČ?

Yes. From 1 January 2023, a data mailbox is mandatory for all OSVČ. You cannot refuse it or close it as long as you hold an active trade licence. Your login credentials were sent to you automatically by post.

What happens if I don't log into my data mailbox?

After 10 days from the delivery of a message, deemed delivery kicks in — the message is considered delivered even if you haven't read it. This means that deadlines start running (e.g. for appeals or payments). Ignoring your data mailbox won't help you — in fact, it can cause you serious problems.

How much does it cost to run a data mailbox?

The data mailbox itself and communication with public authorities is entirely free. You only pay for: sending messages between private entities (approx. 5 Kč per message), SMS notifications (approx. 3 Kč per SMS), and the Data Vault (optional long-term storage).

Can I use my data mailbox for personal matters?

An OSVČ's data mailbox is intended for business use. For personal matters (as a private individual), you can apply for a separate data mailbox for a natural person — this is voluntary and free of charge.

How do I find my data mailbox number?

Your data mailbox ID can be found: in the letter containing your login credentials, after logging in to your data mailbox under Settings, or on the portal info.mojedatovaschranka.cz after logging in.

Can I have more than one data mailbox?

Yes. As an OSVČ, you automatically have a data mailbox for a self-employed individual. You can also voluntarily set up a data mailbox for a natural person (for personal matters). If you also run a limited liability company (s.r.o.), that company has its own data mailbox for a legal entity.

Do I also have to submit reports to ČSSZ and health insurance companies via my data mailbox?

You can submit reports to ČSSZ and health insurance companies via your data mailbox, but you are not required to. The obligation to file electronically applies primarily to tax declarations (tax returns). Reports can still be submitted on paper or through the portals of the relevant institutions.