A UK SMS gateway lets you send business texts from an alphanumeric sender ID of up to 11 characters, and there is no national sender ID registry you are legally required to join. The rules that matter are consent and opt-out: under PECR, every marketing text needs prior consent or the soft opt-in, and every message needs a simple way to opt out.
This guide covers sender IDs, the UK SMS SenderID Protection Registry, Ofcom’s new anti-scam rules for messaging providers, ICO rules on consent and the soft opt-in, opt-out wording, and the encoding and formatting details that decide delivery and cost. For coverage and rates, see our UK SMS gateway page.
Can you use an alphanumeric sender ID in the UK?
Yes. UK networks accept alphanumeric sender IDs made of letters and digits, up to 11 characters, so recipients see your brand name rather than a number. On SMS.to, UK sender IDs are registered with us before live traffic, as shown in our sender ID requirements by country.
Three practical limits apply:
- Alphanumeric IDs are one-way. Recipients cannot reply to a name. If you need replies for surveys, bookings or support, send from a virtual mobile number with two-way SMS instead.
- Pick a distinctive name. Names that resemble banks, government services or delivery firms are likely to be blocked, because those brands protect their sender IDs (see below).
- Keep it consistent. Use the same sender ID for the same type of message so customers learn to recognise it. Changing names between campaigns looks like spoofing.
What is the UK SMS SenderID Protection Registry?
The SMS SenderID Protection Registry is run by the Mobile Ecosystem Forum (MEF). Organisations register the message headers they use, and participating mobile networks and messaging providers block those headers when they arrive from routes the brand has not authorised. MEF says the UK registry started as a proof of concept in 2019 and now holds over 700 trusted sender IDs, with over 3,750 unauthorised variants being blocked.
What this means for you:
- It is voluntary. You do not have to register to send business SMS in the UK. It is mainly used by frequently impersonated brands such as banks and public bodies.
- If your brand is protected, only the providers you authorise can deliver messages under that name. Tell your provider before launch so traffic is not blocked as a spoof.
- If your name is close to a protected brand, your messages may be blocked as an unauthorised variant. Choose a sender ID that is clearly your own.
What do Ofcom’s new rules on scam texts mean for senders?
Ofcom regulates the networks and messaging providers rather than the content of your marketing. On 15 July 2026 it published a statement on combatting mobile messaging scams. The rules require providers to carry out upfront and ongoing Know Your Customer and Know Your Traffic checks on business senders, to prevent fake alphanumeric sender IDs by checking them against KYC information, and to maintain policies on protected and generic sender IDs. According to the statement, the rules for business (A2P) messaging take effect on 15 July 2027.
For legitimate senders, expect your provider to verify your company, to ask you to show that you have the right to use a sender ID, and to refuse generic IDs that could belong to anyone. Having your company details and brand evidence ready shortens onboarding.
When do you need consent to send marketing texts?
The Information Commissioner’s Office (ICO) enforces the Privacy and Electronic Communications Regulations (PECR). The ICO’s electronic mail marketing guidance covers texts as well as emails, and the rules depend on who you are texting and why.
| Scenario | Can you send? | Condition |
|---|---|---|
| Marketing to individuals, including sole traders | Only with permission | Specific consent to texts from you, or the soft opt-in |
| Marketing to corporate subscribers (companies, LLPs, government bodies) | Yes | Identify yourself and give a valid opt-out; keep a do-not-contact list |
| Service messages, such as order updates or appointment reminders | Yes | Must not promote anything; adding marketing turns it into direct marketing |
| Charity fundraising to supporters | Yes, under conditions | Charitable soft opt-in, in force since 5 February 2026 |
The ICO’s key concepts guidance is clear on the service message point: if you add advertising or marketing material to an administrative message, it becomes direct marketing. A delivery update with a discount code at the end needs marketing consent.
The stakes went up in 2026. Following commencement of the Data (Use and Access) Act, the ICO can issue fines of up to £17.5 million or 4% of global turnover under PECR. The same Act introduced the charitable purpose soft opt-in, which came into force on 5 February 2026.
How does the soft opt-in work?
The soft opt-in lets you text existing customers without separate consent. The ICO sets out the conditions:
- The person is an existing customer who bought, or negotiated to buy, a product or service from you.
- You only market similar products or services of your own.
- You gave them a clear chance to opt out when you collected their details.
- You give them a simple way to opt out in every message.
It does not cover prospects, contacts bought from a list, or marketing for other companies. If you cannot show where and how a number was collected, treat it as needing consent.
What opt-out wording should UK marketing texts include?
PECR requires that you do not disguise your identity and that you give a valid, simple way to opt out. For texts, that means your brand name and a working opt-out route in every marketing message.
The route has to match your sender type. A “Reply STOP” instruction does not work from an alphanumeric sender ID, because recipients cannot reply to a name. Use one of these instead:
- An opt-out link. With SMS.to, add the tag
STOPSMS {optout}to your message and it is replaced with a one-click opt-out link on our nosmsto.me domain. The number is then suppressed from your future campaigns. - A reply keyword from a number. If you send from a virtual mobile number, “Reply STOP to opt out” works, as long as you process the replies.
A compliant marketing template looks like this:
AcmeShop: Winter sale, 20% off coats until Sunday at acmeshop.co.uk/sale. Opt out: STOPSMS {optout}
Keep the opt-out short and plain, never charge for it, and stop sending as soon as it is used.
How do you get the best delivery and character count in the UK?
Most UK delivery problems come from formatting and encoding rather than from the networks.
- Stay in GSM-7 where you can. A GSM-7 message fits 160 characters, or 153 per part in a concatenated SMS. The pound sign (£) is part of the GSM-7 set, but the euro sign (€) and characters such as square brackets use two character spaces.
- Watch for Unicode. One emoji, smart quote or accented character not in GSM-7 switches the message to UCS-2, which fits 70 characters, or 67 per part. That can double the number of parts you pay for. Check templates in our Unicode SMS checker.
- Format numbers in E.164. Convert 07700 900123 to +447700900123: drop the leading zero and add +44.
- Use your own domain for links. Generic URL shorteners are widely used in scam texts and attract filtering. A link on your own domain is easier for customers and networks to trust.
- Clean and track. Numbers move between networks, and old lists decay. Use HLR lookups on older lists and a
callback_urlto receive delivery reports for every message. - Send at sensible times. PECR does not set sending hours, but late-evening marketing texts generate complaints and opt-outs. Most senders keep campaigns to daytime and early evening.
For what UK messages cost by volume, see how much an SMS costs by country, and for the rules in other markets, see SMS sender ID rules by country.
How SMS.to handles UK business SMS
With the SMS.to UK gateway, we register your sender IDs before you go live and tell you early if a name is likely to clash with a protected brand. Our opt-out tools add a one-click link to marketing messages and suppress numbers that opt out, and you can rent virtual numbers when you need replies. Every message returns a delivery report to your webhook, and we follow GDPR and can provide a DPA on request. For the data protection side of SMS marketing, read GDPR and SMS marketing: what to watch.
FAQs
Do I need to register my sender ID in the UK?
There is no legal requirement to join a national registry. Your provider will check and register your sender ID before live traffic, and frequently impersonated brands can also protect their names through the MEF registry.
Can I text business customers without consent?
You can send marketing texts to corporate subscribers without consent, but you must identify yourself and offer an opt-out. Sole traders and some partnerships count as individuals and need consent or the soft opt-in.
Does “Reply STOP” work with an alphanumeric sender ID?
No. Recipients cannot reply to a name. Use an opt-out link or send from a virtual number that can receive replies.
Are appointment reminders marketing?
No, as long as they only contain administrative information. If you add a promotion, the ICO treats the message as direct marketing.
What is the maximum PECR fine?
Following the Data (Use and Access) Act, the ICO can fine up to £17.5 million or 4% of global turnover for PECR breaches.
Rules change often. This guide reflects the rules as of September 2026; check with your account manager before launching a campaign.
Planning UK campaigns or alerts? Talk to sales and we will set up your sender IDs, opt-out handling and delivery reporting before your first send.
