City councils can use the personal data contained in the Municipal Register of Inhabitants to identify minors of compulsory school age and get in touch with their families to exercise the powers that correspond to them with regard to the pre-registration process. The tax regulations do not allow the consultation of tax information, in a general way and without the consent of the people affected, in order to be able to detect the existence of specific socio-economic situations prior to the pre-registration application. The compatibility of using other databases or administrative records such as those described in the conduct cannot be ruled out, although the terms in which this exchange of information is described in the query (volume of information, people affected , when it would be carried out, etc.) pose serious problems from the point of view of the proportionality of the measure.