The Municipal Register is the administrative register which records municipality residents. Its formation, maintenance, revision and custody corresponds to the respective town councils. The revision of the municipal register referred to 1 January of each year is obtained from its update.

In 1996 a modification of register regulations was carried out. A new continuous and computerised management system for municipal registers was established, based on the coordination of all of them by the National Statistical Institute.

Based on the aforementioned regulations, the last register renewal was carried out, referred to 1 May, in 1996. This was the starting point for the new register system. The revision to 1 January 1998 was the first update to be carried out in agreement with the new system.

As of this moment official population figures were obtained annually, unlike what occurred previously where population figures were only published every five years for the population censuses - carried out every ten years - or the registry renewals that were carried out every five (the latter were deleted with the new register management system).