The document *Guidelines on Open Access to Scientific Publications and Open Access to Research Data in Horizon 2020* recommends that, "wherever possible, projects should take steps to enable third parties to access, use, reproduce and disseminate (free of charge to any user) the research data". To this end, it is recommended that widely recognised licences be used to define the conditions of use that must be met when the data is to be reused.

Creative Commons 4.0 licences may be used to specify permitted uses. For open research data, the CC0 and CC-BY licences are recommended. Specific data licences, such as those from Open Data Commons, may also be used.

It is important to bear in mind that, depending on the research project and the agreement with the project’s funding agency, it may be necessary to apply a embargo period during which the data cannot be accessed for the required duration. Alternatively, the agency may explicitly specify the mandatory deadlines for public dissemination and under what terms.

Furthermore, in line with the general principle of “As open as possible, as closed as necessary” contained in the Guidelines on FAIR Data Management in Horizon 2020, there are situations that justify not making research data openly available, such as: the existence of confidentiality clauses, the possibility of commercial or industrial exploitation, etc.