Since 2015 Portugal has more strictly enforced a long-standing law requiring anyone providing paid holiday accommodation to record the entry, exit, and identification details of all non-Portuguese nationals who use that accommodation. This law has been brought into force in Portugal and most other EU countries at some point since the gradual implementation of the 1990 Schengen Agreement that aims to stop human trafficking and other illegal practices. In this case, it is specifically Article 45 of the Schengen Agreement and the recent Alojamento Local law in Portugal that has brought this rule into sharper focus.
For this reason, all guests of every reservation need to allow the collection of the required information.