Spain’s 400-prefix law will make it harder to reach customers

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.