The monitoring system must be set up in a way that it permits the managing authorities to perform the tasks related to monitoring and evaluation as set out in Art. 56 CPR (Regulation (EU) No 1303/2013) and Articles 5 and 19(4) and (6), Annex I and II of the ESF Regulation (Regulation (EU) No 1304/2013). This implies that all participant records should include some sort of unique personal identifier that allow an individual to be traced and re-contacted (in case they are selected for a representative sample), as well as the operation identifier and dates of starting and leaving the operation. Personal identifiers can be used to link ESF monitoring data with records from national registers, but this is not a requirement.