New SMS rules: the CNMC's Alias Registry

This article is informational and does not constitute legal advice. Check the current deadlines and requirements before planning your campaigns.

If your business sends SMS with an alphanumeric sender (a name instead of a number, such as "MYBRAND"), there's a regulatory change you need to know about: the CNMC's Alias Registry.

Why this regulation exists

The alphanumeric sender was easy to forge, and that flexibility was widely exploited for smishing: SMS scams in which criminals impersonate banks, logistics companies or public administrations to steal data or credentials.

To tackle this, Order TDF/149/2025 and, developing it, the CNMC's Circular 1/2026, of 18 March (published in the BOE on 27 March 2026) regulate the Alias Registry.

What changes and from when

The blocking obligations were initially set for 7 June 2026, but Order TDF/558/2026, of 4 June, postponed them to 15 September 2026. From that date, operators involved in message transmission must block SMS that:

• have an alias not registered in the Alias Registry, or
• even if registered, do not arrive from providers authorised to use that alias.

In practice: if your alias is not registered, your SMS could stop being delivered.

Alias requirements

The circular sets criteria for alphanumeric senders in SMS and MMS:

• length of 3 to 11 characters,
• letters, numbers and certain specific symbols are allowed,
• purely numeric strings, excessive special characters and aliases that may cause confusion are excluded.

In addition, you must prove a legitimate link between the alias and your company: registered trademark, trade name, company name, registered domain or other names entered in public registries.

What you should do

• Take stock of the aliases your company uses for SMS.
• Register them and make sure you can prove their legitimate link.
• Send through providers authorised for those aliases.
• Plan ahead: from 15 September 2026, unregistered aliases are blocked.

At Virtual Voz we help you adapt your messaging to the new regulation. If you send SMS with a branded sender and want to make sure you comply, get in touch.