We are just days away from the implementation of a new regulation that is sure to affect businesses in Spain that make outbound calls: the requirement that commercial calls must use a 400 prefix.
The 400-prefix requirement is just one piece of the broader Customer Service Law (often referred to as “Ley SAC”) that was adopted on December 26, 2025 in an effort to both improve the customer service experience and to reduce spam calls. A resolution published in April 2026 provides details of the 400-prefix requirement.
There seems to be some confusion over what the regulation does and does not require. Let’s start with an overview of the major elements of the regulation.
The new 400-prefix regulation follows other regulatory measures introduced in Spain, such as the prohibition on using mobile numbers for certain commercial calls. That measure, which took effect in June 2025, was intended to prevent businesses from using mobile numbers that could give the impression that the call was coming from a private individual, friend or acquaintance.
It’s obvious that the 400-prefix regulation is going to have a huge effect on call centers and any business that makes outbound sales calls. One of the problems is that all commercial calls will be lumped together in the same bucket.
Based on what we have seen in markets where similar regulations have been introduced, consumers are very likely to see a 400-prefix number on their phone screen and simply ignore the call. And we can hardly blame them, because they have no way of knowing whether the call is coming from a business they actually want to speak to, a fraudulent company, or one they would simply prefer to avoid.
That’s why Hiya recommends that businesses use branded caller ID, which displays the business name, phone number and reason for the call on the recipient’s mobile device. The phone number will still display the 400-prefix, but if consumers can see exactly who is calling and why, they may be more likely to answer — or return the call when it’s convenient for them.
You can learn more about branded caller ID at the bottom of this blog post, but first l’d like to address some of the frequently asked questions about the new regulation.
The 400-prefix regulation was approved in April 2026, and businesses have six months to fully comply, meaning they have until October 17, 2026. This measure is part of the overall Customer Service Law, which was passed on Dec. 26, 2025. Most of the other measures within the Customer Service Law require compliance within one year, meaning by the end of December 2026.
The 400-prefix regulation applies to businesses defined in the broader Customer Service Law:
Specific rules also apply to certain sectors and services considered to be of general interest.
In addition to companies themselves, the measure also applies to contact centers that make outbound commercial calls on behalf of businesses. Mobile network operators are also affected by the regulation, as they have the responsibility to make the 400-prefix available to businesses and to block commercial calls that do not include the 400 prefix.
Businesses that make commercial calls from non-400-prefix numbers will have their calls blocked. Failure to comply may also result in financial penalties, and the business may have to compensate consumers if it has caused them harm.
The aim is to avoid confusion and reduce certain risks associated with returning calls. Consumers can contact businesses through the customer service channels provided for that purpose, including toll-free numbers where applicable.
As you can imagine, businesses are concerned that consumers will simply ignore calls that begin with the 400 prefix. That’s what happened when a similar law was enacted in Brazil.
“The adoption of the prefix had a significant negative impact on several operations, with answer rates decreasing by 30% to 50%, said Thiago Peixoto, Commercial Director of GoSat, which provides contact center outsourcing. “In some cases, unfortunately, this scenario even contributed to companies shutting down their operations in Brazil.”
One way to counteract reduced answer rates is to identify who is calling. According to Hiya’s State of the Call survey, only 13% of Spanish consumers say they answer calls from numbers they don’t recognize. On the other hand 47% of Spaniards say they would be likely or very likely to answer a call where the caller is clearly identified.
So if you’re worried that the new 400-prefix regulation is going to lower your answer rates, one of the best things you can do is to identify your calls using branded caller ID. Branded caller ID enables businesses to display their name, logo, and reason for the call directly on the recipient’s screen.
And unlike traditional caller ID, which was built for landlines and is susceptible to scammers spoofing phone numbers, companies using branded caller ID must go through a vetting process to prove their legitimacy.
Hiya Branded Call is compliant with Spain’s regulations, and can increase answer rates by up to 50% compared to anonymous calls.
Don’t let your important business calls go unanswered! Learn more about Hiya Branded Call or give us a call to talk to a member of our team in Spain.