Spain Enforces 400 Prefix for All Commercial Calls

By Elena Vasquez

Since Saturday, 17 October, every commercial call in Spain must originate from a nine-digit number beginning with 400. Any sales call placed from an ordinary mobile or geographic number is now illegal, and operators such as Movistar, Orange, Vodafone and Digi are obliged to block it on their own networks.

The measure implements the Customer Service Services Law (Ley SAC) and forms part of the Plan Against Telephone and SMS Scams promoted by the Ministry for Digital Transformation and the Civil Service. It is the latest step in a programme that, according to official data, has already blocked more than 400 million fraudulent calls and close to 32 million text messages since it began in 2025.

What does the 400 prefix change for consumers?

The 400 range consists of full nine-digit numbers, not short codes. Its purpose is simple: a consumer should know a call is commercial before answering it. Think of it as a caller ID line painted on the number itself.

These lines work in one direction only. A user cannot call a 400 number back, a deliberate design choice meant to prevent fraudsters from luring people into returning calls to unknown lines.

The prefix flags the commercial nature of the contact, but it does not identify the company behind it. Businesses must still identify themselves and explain their offer during the conversation.

Because the prefix alone leaves the caller anonymous, the industry association Adigital moved ahead of the deadline with Soy Yo, a free reverse lookup service. Participating companies register their 400 numbers there, and users can check who is behind an unknown call.

How will operators police the new rule?

Blocking is not optional. Movistar, Orange, Vodafone and Digi must detect and stop commercial traffic that continues to flow from ordinary mobile or geographic numbers.

To find that traffic, operators will rely on algorithmic systems that spot patterns typical of call centres. The criteria include a high volume of calls to many destinations in a short time, and calls that are hung up instantly.

These technical criteria require prior authorisation from the State Secretariat for Telecommunications before operators deploy them. According to the portal Banda Ancha, Digi has confirmed it will also display an on-screen warning reading "Llamada comercial" or the company's name whenever a call arrives from a 400 number.

What about customer service calls?

The regulation draws a clear line between sales prospecting and customer service. Calls that manage existing contracts will continue to come from specific short numbers, from the free 800 and 900 ranges, or from ordinary geographic lines.

There is one further restriction. Companies may no longer use customer service calls to pitch products, unless the offer is directly linked to resolving the customer's query or issue and represents an improvement in price or conditions for the user.

Where can consumers complain?

Anyone who receives a commercial call from a number outside the permitted ranges has two routes for redress. They can file a claim with the Telecommunications User Care Office (OAUT), or lodge a complaint with the National Commission for Markets and Competition (CNMC).

The 400 prefix sits within a broader enforcement effort that has gathered pace this year. On 15 September, the CNMC's alias registry for alphanumeric sender codes on SMS, MMS and RCS came into operation. That registry alone has already led to the blocking of more than six million unauthorised messages.

For Spain's operators, the immediate work is technical: deploying detection algorithms, securing regulatory sign-off and filtering non-compliant traffic. For the Ministry, the next test will be whether the 400 prefix, combined with mandatory blocking, produces a measurable drop in nuisance and fraudulent calls over the coming months.