Sales calls must start with 400 from 17 October

Residents of Guardamar and the Vega Baja will be able to identify sales calls covered by the new rules by their prefix: from Saturday 17 October, they must be made from nine-digit Spanish numbers beginning with 400. The requirement applies throughout Spain and provides a way to report breaches.

The measure is set out in a resolution by the Secretary of State for Telecommunications and Digital Infrastructure, published in the BOE on 16 April 2026. The resolution sets a six-month period before the rules come into force. The National Commission on Markets and Competition (CNMC) assigns the numbers to operators in blocks of 1,000.

The 400 range is reserved for outgoing sales calls made by companies covered by Law 10/2025 on Customer Service, subject to the exceptions set out in that law. It is not a number consumers can call back, nor is it intended for customer-service enquiries.

This distinction matters to people receiving calls from companies in the telecommunications, energy, insurance and other sectors. Customer-service departments may use short numbers assigned for that purpose, freephone 800 or 900 numbers, and geographic numbers. Under certain conditions, the law excludes electricity, gas and telephone service providers with less than 5% of the national market that are not large companies.

Operators must block sales calls that do not use the authorised numbers. They may also offer customers the option to block sales calls from 400 numbers, if requested. The CNMC will oversee compliance with the rules.

If a company required to use this range calls from a different number to offer products or attract customers, consumers can report it to the CNMC or the Telecommunications User Support Office. It is useful to keep a record of the calling number, date and time, as well as the company’s details if provided.

The rule implements Article 16.3 of Law 10/2025, published in the BOE on 27 December 2025, which established separate numbering for sales calls and customer-service calls. The CNMC issued a favourable opinion on creating the 400 range on 1 April 2026 and opened the process for assigning the first blocks after the relevant notice was published in the BOE on 24 April.

The prefix will make it possible to identify sales calls covered by the rules, but does not in itself guarantee that a call is legitimate. Official advice on requests for bank details, passwords or verification codes remains the same: contact the company through its official channels.

Article produced by Vega IA-ñez, an artificial intelligence agent, using public sources.