Spain

To send SMS to Spanish numbers with an alphanumeric sender, that sender must be registered with the CNMC (Comisión Nacional de los Mercados y la Competencia), in its Sender Alias Registry. Registration is equally mandatory for RCS, as an alias independent of the SMS one — registering one does not include the other. It applies to RCS now, not from some later date — see Does it apply to RCS too?.

On SMS, the filing is for alphanumeric senders — the ones that carry your brand. A sender that is a valid international phone number is exempt and does not go through the CNMC; a string of digits that isn't a phone number — 123, say — is not. It is a valid way out if you need to send to Spain before your alias is cleared, at the cost of your messages arriving from a number instead of under your name. On RCS there is no exemption: your agent's alias goes through the CNMC either way.

How registration works

Registration has two parts, and each one is done by a different person: the alias details are provided (the brand, the owner, the legal representative) and then the legal representative authorises the alias at the CNMC. The CNMC always notifies the legal representative, so their details have to be correct.

How to register your alias: two paths

You can register the alias in two ways, and both end with the legal representative authorising it at the CNMC's electronic office:

The Filing step in the sender request

Spain adds one extra field to the country request you submit on the sender (the generic flow is in SMS senders & registration). When you request Spain, the form shows a Filing choice for the CNMC:

• I'll file it myself — the recommended option, and the one selected by default. Pick it if you've already registered the alias with the CNMC yourself (see Registering your alias directly), and supply the proof.
• Instasent files for you — Instasent submits the alias to the CNMC registry on your behalf. Your legal representative still has to authorise it at the CNMC (see Authorising the alias at the CNMC).

The sender request also shows a card titled Spain · CNMC with the notice: This country is regulated by CNMC, which will require every sender to be registered from 15 September 2026. After that, operators block messages from senders without a valid registration. Completing this step registers yours ahead of time.

Send the alias exactly as you filed it

The check against the CNMC registry is literal: character by character, capitals included. Nothing is normalised.

If you filed PEDRO and you send Pedro, as far as that check is concerned your alias isn't filed — with the consequences of not being filed, even though the procedure went through and was approved.

It is the hardest failure of all to diagnose, because everything looks right: the register shows as approved, the CNMC has your alias, and the messages still don't arrive as they should. Before investigating anything else, compare the spelling.

Alias rules

Length	3 to 11 characters
Allowed	letters a–z and A–Z, digits 0–9, and @ & - _ . +
Not allowed	numbers only, accented characters (á, é, í…), the symbols ! ? # % * € ( ) [ ], and generic names ("Banco", "Mensaje", "Urgente")

The alias must be genuinely and legitimately tied to your brand. The CNMC may reject one that is generic or that could cause confusion, fraud or impersonation.

Does it apply to RCS too?

Yes. Registration with the CNMC is also mandatory for RCS, and it's a registration independent of the SMS one: the SMS alias and the RCS alias are registered separately, and registering one does not include the other. The CNMC portal already covers it — the direct self-registration lets you choose the message type (SMS/MMS or RCS).

The RCS agent goes through the CNMC just like an SMS sender, and you file it now rather than on the deadline: the CNMC can take up to a month to resolve a filing, so a register submitted on 15 September arrives late. Your RCS register carries its filing type and its legal profile from the moment you submit it — there is nothing to wait for.

With RCS, the agent also has to be approved by the operators, and you need an enabled provider for RCS in Spain. You configure the RCS agent in RCS senders & verification.

Regulation

Alias registration comes from Spain's messaging regulation, designed to curb fraud (smishing) and impersonation:

• Orden TDF/558/2026 — sets the obligation and the date (15 September 2026).
• CNMC Circular 1/2026 — regulates the registry and the alias format (what can be registered, non-generic names).
• CNMC Circular 2/2026 — amends the previous one to allow acting through an authorised representative by means of an authorisation letter.
• CNMC electronic office — Sender Alias Registry management and the official registration guide.

What this country needs

SMS

• Regulator — CNMC
• Your sender — Your alphanumeric sender is accepted as it is.
• What they ask for — Registration with a regulator
• Who acts — Either we file it for you, or you file it yourself.
• Have this ready — A valid Spanish electronic certificate, or an authorisation letter; An alias of 3 to 11 characters, not generic
• How long it takes — up to a month
• Without an approved registration — Messages still go out and are still billed, but delivery is best-effort: the recipient may see a sender other than yours, and the message can be filtered. You keep seeing your own sender in reports and exports — what changes is what reaches the handset.

The CNMC filing has its own guides, with the two available paths and what to do if the alias is refused. A numeric sender — a valid international phone number — is exempt.

RCS

• Regulator — CNMC
• What they ask for — Registration with a regulator
• Who acts — Either we file it for you, or you file it yourself.
• Have this ready — The same CNMC requirements as SMS, with an independent alias
• How long it takes — up to a month
• Without an approved registration — Nothing is sent to this country until the registration is approved.

The RCS alias is registered with the CNMC independently of the SMS one: registering one does not cover the other. There is no numeric exemption here.

Step by step