UK SMS sender IDs: how sender names work

Normally a text shows the number it came from. With an alphanumeric sender ID the phone shows a name in that spot, and most phones group the texts from that name into one thread.

There is no number behind the name, which is why nobody can reply. The name is a label the sender sets, and the recipient's phone has nowhere to send an answer.

The 11-character ceiling comes from the SMS standard itself. TS 23.040 allows 12 octets for the whole sender address field, and once the length and type octets are taken off, the 10 that remain hold 11 GSM-7 characters.

In CaptiFi Connect a sender name is 3 to 11 characters. It can use letters, digits, spaces and the symbols . & _ -, and it needs at least one letter.

Eleven characters go quicker than you'd think. Plenty of business names need shortening, and the right short version is usually the one customers already use, whatever is on your sign or your receipts.

The Mobile Ecosystem Forum (MEF) runs the SMS SenderID Protection Registry to fight smishing, the scam texts that appear to come from a trusted sender, such as a bank or a government department, to get money or account details out of people. Organisations register the sender names they use, and the registry lets the industry check whether a text using one of those names comes from the genuine registered party. It also keeps a growing list of unauthorised variants of registered names, which are blocked.

If you're sending honest texts, the registry still affects you: a name that's close to a registered brand will be refused. If it's your own brand being copied, MEF's page says mobile operators, banks, government agencies and messaging providers with a direct connection can sign up, so that's the place to start.

On 15 July 2026 Ofcom finalised new rules on scam texts. For business messages, mobile operators and the aggregators that carry business traffic must run 'Know Your Customer' checks on new senders and 'Know Your Traffic' checks on what they send, and they must prevent fake sender names by checking each one against what they know about the business. Ofcom's own example of a warning sign is a supposed hairdresser sending parcel delivery texts.

The same rules cover person-to-person texting, where mobile providers must block numbers used by scammers and set volume limits on pay-as-you-go SIM cards. That's one more reason business texts at volume go through A2P routes, where the sender has been checked.

Operators and aggregators must also keep a policy on protected sender ID lists and on generic names such as 'customer service'. In practice, a sender name has to make sense for the business using it. A clear, specific name that matches your business is the easiest kind to get approved, now and as these rules settle in.

In CaptiFi Connect, these are the reasons a name gets refused:

Use a sender name when the text is one-way and recognition matters: appointment reminders, delivery updates, booking confirmations, campaigns. Use a number when you want something back.

In CaptiFi Connect, one-to-one texts sent without a sender name go out from a real UK mobile number, and replies come back to your inbox threaded by number. Campaigns, and anything sent from a sender name, go through a licensed A2P route, which is the route built for business texts. A campaign goes out under the approved sender name you pick, or under our default sender if you leave it on Default.

Every name is checked by our team before it can be used, including against the MEF SenderID Protection Registry, and we ask what each name is for when you request it. We won't approve a name that imitates another brand or a public body.

No. A text from a sender name is still electronic mail under PECR, so marketing needs consent or the soft opt-in, and every marketing text needs a simple opt-out. Regulation 23 also bans marketing where the sender's identity is disguised or concealed, which is one more reason the name should be plainly yours.