For monitoring purposes there is no flexibility as regards the completeness requirement. In order for a participant to be counted, information should be complete for all non-sensitive personal variables: gender, employment status, age, level of education and household situation.
The only variables that can be incomplete are those dealing with special categories of personal data (i.e. sensitive data) that are required for indicators marked with “**” in Annex I of the ESF Regulation (Regulation (EU) No 1304/2013) (i.e. those related to migrants, participants with a foreign background, minorities, participants with disabilities, and other disadvantaged). For these variables, if the participant refuses to provide the information then it can be left empty but the managing authority should maintain documentary evidence that they have attempted to collect the information (see section 5.6 in Annex D of the EC Guidance document).