Spain makes 400 prefix mandatory for all commercial calls

From Saturday, operators will block commercial calls not made from numbers starting with 400. This numbering is reserved exclusively for customer acquisition and cannot be used for customer service or after-sales services.

The requirement comes into force this Saturday. Telecom operators will have to block all commercial calls aimed at acquiring new customers that are not made from numbers beginning with **400**. The measure implements Spain's customer service law, which came into force in **December 2025**, and complements the government's plan against phone and SMS scams, launched in **March of that same year**.

## What changes for businesses and users

Companies covered by this requirement must use nine-digit numbers starting with **400**. These numbers will be reserved exclusively for commercial calls. The order expressly prohibits using this numbering for customer service or after-sales services. They will only allow outgoing calls, so users will not be able to call back.

If someone receives a commercial call from a different number, they can report it to the **Comisión Nacional de los Mercados y la Competencia** (CNMC), Spain's competition and markets watchdog, which is responsible for overseeing compliance with the resolution. The law gives companies within its scope until **December 2026** to adapt their services.

## The CNMC has already allocated 98,000 numbers

To prepare for the rollout of the 400 prefix, the CNMC launched an initial allocation procedure for operators last **April**. It awarded **98 blocks of 1,000 numbers**, a total of **98,000**, according to sources at the market regulator. It also set the conditions for networks to be ready to carry these calls within the planned timeframe.

The order also enabled the **800** and **900** ranges for these communications, so that users could return the calls free of charge. Since **2023**, Spain's general telecommunications law has recognised the right not to receive unwanted commercial calls, unless there is prior consent or another legal basis legitimising them, as established under data protection rules.

## Service in under three minutes and more than 400 million calls blocked

Spain's customer service law requires that **95%** of incoming calls be answered, on average, in under **three minutes**. It guarantees that customers can request to speak to a person, without the service depending exclusively on automated systems, according to the law itself. Since **June 2026**, mobile numbers have been banned from providing customer service or making unsolicited commercial calls.

The anti-scam plan, developed in cooperation with the main operators, has blocked more than **400 million calls** and **32 million fraudulent messages**, according to figures released by the **Ministerio para la Transformación Digital y de la Función Pública** (Spain's digital transformation ministry). The plan also includes an alias registry managed by the CNMC to identify companies and public administrations that send messages using a name instead of a phone number.

Since **15 September 2026**, operators must block messages with unregistered aliases or sent by unauthorised providers. In its first month in force, this requirement has blocked more than **six million messages** from unregistered senders, according to the ministry.

If you receive a commercial call from a number that does not start with 400, you can report it to the CNMC. For any questions about your rights as a consumer, it is advisable to check the current rules or consult a specialised professional.