Different rules apply in Slovakia and Czechia. In Slovakia, you may call with an offer, generally using a number reserved for marketing, if the number called is not on the opt-out register maintained by the regulatory authority and the recipient has not objected to such calls from you. You must check the numbers against the register before the campaign. In Czechia, you must not make marketing calls to numbers from public or purchased lists, or to randomly generated numbers, unless their holder, including a company, has opted in to marketing calls. When calling individuals, including sole traders, you need a legal basis under the GDPR in both countries and must inform the recipient of the right to object no later than during the first call.
A company obtains a contact list from a database or the internet and wants to use a call centre to offer services to individuals and companies it has never worked with. The Slovak Electronic Communications Act uses a register of those who do not want calls. By contrast, for numbers from lists, the Czech Act permits calls only to those who have opted in to marketing calls. Regulation (EU) 2016/679 (GDPR) also applies in both countries because an individual’s telephone number is personal data too.
In Slovakia, the opt-out register is decisive
The Regulatory Authority for Electronic Communications and Postal Services maintains on its website a register of telephone numbers whose holders do not consent to calls for direct marketing purposes (Section 116(7) of Act No. 452/2021 Z. z. on Electronic Communications). Entry in the register triggers a prohibition:
The following quotation is reproduced in its original language:
Na účely priameho marketingu je zakázané akékoľvek volanie, ak účastník alebo užívateľ uviedol telefónne číslo v zozname alebo, ak účastník alebo užívateľ namietal takéto volania osobe, v prospech ktorej sa vykonáva priamy marketing.
The prohibition does not apply if the recipient gave you consent after the most recent update to the entry for their number. The Act makes no distinction between individuals and companies for the purposes of the register. Any subscriber or user may register, and entries take effect on the first or sixteenth day of the month. You must therefore check numbers before every campaign. Checks are subject to a fee (Section 116(10)) and are made through an account that the company carrying out direct marketing registers using the authority’s application interface (Section 2(2) of Decree No. 368/2022 Z. z.). Opt-outs apply to individual categories, such as energy, financial services or property sales (Section 4(2) of the Decree), so the result of the check also depends on what you offer.
In addition to checking the register, you must comply with further rules:
- for marketing calls, you may use only numbers reserved for that purpose by the numbering plan, except when calling published contact numbers of entrepreneurs and legal entities (Section 116(12)),
- the Act prohibits calling solely to obtain consent (Section 116(4)),
- automated calling systems without human intervention, SMS messages and emails require prior consent that you can demonstrate, unless a statutory exception applies (Section 116(3) and (15)),
- if the recipient objects to the call, you must acknowledge receipt of the objection within 30 days at the latest in a way that you can demonstrate, retain that acknowledgement on a durable medium for at least 4 years (Section 116(6)) and stop calling them.
The register and reserved-number requirements do not apply to offers of your own similar goods and services to customers whose contact details you obtained during a sale or with whom you have a contractual relationship, or to anyone who has demonstrably requested such communications in advance. Even then, however, you must offer an opportunity to refuse communications when obtaining the contact details and at every subsequent contact (Section 116(14)), and you may use the contact details in this way for 1 year after the contractual relationship ends (Section 116(16)). Breaching these obligations is an administrative offence for which the authority imposes a fine on the business (Section 124(3)). For email offers, the question newsletters to existing customers without consent explains the exceptions.
In Czechia, opting in through a public directory is decisive
Czech Act No. 127/2005 Sb. on Electronic Communications prohibits offering goods or services through electronic communications networks and services to subscribers who have not indicated in a public directory that they wish to be contacted for marketing purposes (Section 96(1) of Act No. 127/2005 Sb.). A list of numbers without any further details and randomly generated numbers are also treated as a subscriber directory (Section 95(5)). The rule also applies to subscribers that are legal entities (Section 96(4)). Anyone calling numbers from a purchased list or generated numbers needs their holders to have opted in to marketing calls in advance, for example through their operator.
In its guidance on marketing calls, the Czech Telecommunication Office states that the Electronic Communications Act addresses cases where the source of the contact is a public directory, including randomly generated numbers. Calls to clients from a customer database and, according to the Office, the use of an entrepreneur’s number published on the internet are governed by personal data protection rules, supervised by the Czech Office for Personal Data Protection.
GDPR in both countries
If you call an individual, including a sole trader, you process their personal data. A legitimate interest may provide a legal basis (Article 6(1), letter f) GDPR), but it must be assessed and documented in advance. If you did not obtain the contact details directly from the recipient, you must provide information about the processing, including the source of the data, within a reasonable period and no later than 1 month after obtaining the contact details. If you contact the person sooner, they must receive the information no later than at the first contact (Article 14(3), letters a) and b)). No later than at the first contact, you must expressly draw their attention to the right to object, separately from other information (Article 21(4)). If they object, you must no longer use their data for marketing (Article 21(3)).
We will help you structure the campaign according to the country you are calling. We will assess the source of the contacts and prepare a call script containing the information required by the GDPR, a procedure for checking numbers and an objections register as part of our GDPR and personal data protection service.
This answer provides general information on the law as at 3 October 2026. It does not constitute legal services or replace an assessment of an individual case. The details of your situation may differ. Book a consultation to discuss them.
