In Spain, the regulations governing commercial telephone communications are undergoing a major transformation. Designed to strengthen consumer protection and improve the identification of commercial calls, the new Spanish regulation provides for the implementation of dedicated numbering for making commercial calls.
As of October 17, 2026, concerned commercial calls must be made from dedicated numbering belonging to the 400 prefix, in accordance with the provisions of BOE No. 93 of April 16, 2026.
This new numbering is exclusively reserved for making commercial calls to consumers. 400 numbers cannot receive inbound calls and cannot be used within the context of customer relations.
Compliance with this new 400 numbering therefore represents an essential issue to ensure the continuity of commercial call campaigns in Spain and to avoid using non-compliant numbering at the end of the transition period.
1. Legal framework: why and how does the law make the 400 prefix mandatory?
The implementation of the 400 prefix stems from Ley 10/2025 de Servicios de Atención a la Clientela (SAC) and the resolution of the Secretaría de Estado de Telecomunicaciones e Infraestructuras Digitales published in the BOE on April 16, 2026.
This regulation addresses several major objectives of user protection and market regulation:
Immediate identification and transparency: Setting up a dedicated prefix starting with 400 allows users to immediately identify a commercial communication upon receiving the call.
Strict separation of channels: Spanish regulations establish a distinction between numbers used for customer service and those used for outbound commercial calls. Since the resolution of April 16, 2026, the 400 prefix is specifically assigned to commercial calls. Companies falling within the scope of Ley 10/2025 can no longer use another number block for their commercial calls to end consumers.
2. Operating in prospecting: unidirectionality and voicemail blocking
Starting October 17, 2026, any commercial solicitation aimed at end consumers must be made using the mandatory 400 prefix.
This measure results in usage constraints:
Strict unidirectionality (Outbound calls only): the 400 prefix is dedicated to outbound commercial calls. Numbers belonging to this block are reserved for making these calls and do not allow inbound calls to be received.
Inability to call back: since the 400 block is exclusively dedicated to outbound commercial calls to consumers, the numbers concerned cannot be reached for inbound reception. Therefore, a callback by a consumer to a 400 number cannot be routed as an incoming call. The 400 number is automatically blocked by telecom operators.
Voicemail blocking: Any promotional or commercial communication delivered through a voice call (whether handled by a human operator or an automated pre-recorded message/voicemail campaign or marketing campaign) falls under the regulation of the State Secretariat for Telecommunications.
Commercial calls require prior consent or an existing contractual relationship (rule in effect since June 2023). Consult the Robinson list and the GDPR.
3. How to obtain a 400 number?
The prerequisites for obtaining a 400 number are as follows:
Required information:
First and last name
Contact phone number
Company name
Copy of the company registration certificate
Proof of address verification:
Address in Spain (street, building number, postal code, city, and country)
Copy of a utility bill (electricity, water, gas, etc.) dated within the last 6 months
Pricing:
The rate will be identical to that applied for a Spanish national number.