Since 17 October 2026 companies in Spain must make commercial telephone calls from nine-digit numbers with the 400 prefix The nationwide requirement stems from a resolution published in April 2026 by the Secretaría de Estado de Telecomunicaciones e Infraestructuras Digitales and is intended to better protect consumers from unwanted or fraudulent advertising calls. On 25 October, the Gobierno de Cantabria explained the requirements again and offered advice on dealing with telephone offers.
The rule clearly distinguishes between advertising and service purposes: marketing and sales contacts must use the 400 range. By contrast, freephone numbers with the 800 and 900 prefixes, as well as geographically designated landlines, remain reserved for customer service, complaints and support for existing contracts. Network operators must implement the number ranges technically and block calls that serve commercial purposes but do not originate from the 400 range.
The measure was published in the Boletín Oficial del Estado ; deadlines and technical requirements are also set out there. The Ministerio para la Transformación Digital y de la Función Pública had reminded companies of the changeover in the spring and shortly before the deadline. Consumer organisations warn that the 400 prefix only identifies the type of call and says nothing about whether it is legitimate. They recommend caution, keeping a record of suspicious contacts and, where appropriate, blocking them.
For companies, the requirement means adapting call-centre infrastructure, dialling software and caller ID. Network operators are required to provide filtering and blocking mechanisms and report misuse. For users, the 400 prefix makes advertising calls immediately recognisable and makes it easier to set individual blocking or filtering preferences.
Regional administrations, including Dirección General de Comercio y Consumo in Cantabria, are sharing additional guidance on rights relating to advertising calls. These include the right to object to telephone marketing at any time, transparent identification of the caller at the start of the conversation, and the requirement to keep verifiable records of consent to be contacted. Breaches may be punished as unfair competition or as violations of data protection and consumer law.
Implementation over the coming months will depend largely on how consistently companies adapt their numbers and how effectively network operators filter unlawful calls. Authorities have announced spot checks; the practical effectiveness of the system will also be judged by whether it can successfully curb deception using spoofed caller numbers.
Editor: Mira Cadena (Article created with AI assistance).