The law of conservation of data on electronic communications and public communications networks (Law 25/2007 October DE18) states that service operators should maintain a prepaid telefoníamóvil logbook stating laidentidad customer. Data may be required by order of a judge, in order to detect, investigate and prosecute serious crimes.

 This provision came into force on November 9, 2007. From that date, people who buy prepaid cards are required to identify in the register of operators.