Spain to mandate 400 prefix for commercial calls to combat fraud

Spain is implementing new telecommunications regulations to combat fraudulent and unsolicited commercial calls. Starting October 17, 2026, all commercial telephone calls must originate from a nine-digit national number beginning with the 400 prefix.

These 400-series numbers are designed to be outgoing only; telephone operators will block incoming traffic to this range, preventing recipients from calling back unknown numbers and potentially landing on fraudulent lines. This measure aims to reduce the risk of scams associated with returning calls from unfamiliar mobile or geographic numbers.

Telephone operators will also be required to block commercial calls made from mobile, geographic, 800, or 900 numbers that do not comply with the new prefix requirement. Additionally, providers may offer customers the option to block the entire 400 range to silence all commercial calls at once.

While the new prefix identifies marketing calls, businesses must still adhere to existing data protection and marketing laws, requiring valid consent or legal grounds to contact individuals. Customer service calls will remain subject to different rules and may continue to use approved short numbers or landlines. Consumers can report non-compliant calls to the Telecommunications User Service Office or the CNMC.