United Kingdom SMS Best Practices, Compliance, and Features

United Kingdom SMS Market Overview

Locale name:	United Kingdom
ISO code:	GB
Region	Europe
Mobile country code (MCC)	234, 235
Dialing Code	+44

Market Conditions: The UK has a mature and sophisticated SMS market with high mobile penetration rates. Major mobile operators include EE (BT), Vodafone, O2 (Telefonica), and Three. While OTT messaging apps like WhatsApp and Facebook Messenger are popular for personal communications, SMS remains crucial for business communications, particularly for authentication, notifications, and marketing. The market shows a relatively even split between Android and iOS users, with both platforms well-represented.

Key SMS Features and Capabilities in United Kingdom

The UK supports a comprehensive range of SMS features including two-way messaging, concatenated messages, and number portability, with strong carrier infrastructure for reliable message delivery.

Two-way SMS Support

Two-way SMS is fully supported in the UK with no significant restrictions. Businesses can engage in bi-directional communications with customers, making it ideal for customer service and interactive campaigns.

Concatenated Messages (Segmented SMS)

Support: Yes, concatenation is fully supported across all major UK carriers.
Message length rules: Single SMS supports 160 characters (GSM-7) or 70 characters (Unicode). Messages exceeding these limits are automatically concatenated.
Encoding considerations: GSM-7 encoding is standard for basic Latin alphabet, while Unicode (UCS-2) is used for special characters and non-Latin alphabets, with reduced character limits.

MMS Support

MMS messages sent to UK numbers are automatically converted to SMS with an embedded URL link to the media content. This ensures compatibility across all devices while maintaining the ability to share rich media content.

Recipient Phone Number Compatibility

Number Portability

Number portability is fully available in the UK. Users can retain their mobile numbers when switching between carriers, with minimal impact on SMS delivery or routing.

Sending SMS to Landlines

SMS to landline is supported in the UK, with messages typically converted to text-to-speech for landline recipients. However, Virgin Mobile no longer supports SMS to UK landline numbers, and delivery success can vary by carrier.

Compliance and Regulatory Guidelines for SMS in United Kingdom

SMS communications in the UK are regulated by the Information Commissioner's Office (ICO) under the Privacy and Electronic Communications Regulations (PECR) and the General Data Protection Regulation (GDPR). The primary regulatory framework focuses on consent, data protection, and consumer rights.

Explicit Consent Requirements:

Must obtain clear, specific opt-in consent before sending marketing messages
Consent must be freely given, specific, informed, and unambiguous
Pre-ticked boxes or assumed consent are not compliant
Keep detailed records of when and how consent was obtained
Consent must be refreshed periodically (recommended every 24 months)

HELP/STOP and Other Commands

All marketing messages must include a clear opt-out mechanism
Required Keywords: STOP, UNSUBSCRIBE, END, QUIT
Messages must be in English; additional languages permitted but English is mandatory
Opt-out mechanisms must be free of charge to the consumer
HELP responses should include company information and contact details

Do Not Call / Do Not Disturb Registries

The UK maintains the Telephone Preference Service (TPS) and Corporate TPS registries
Mandatory Compliance: Must screen numbers against TPS before sending marketing messages
Maintain internal suppression lists of opted-out numbers
Process opt-out requests within 28 days maximum (immediate processing recommended)
Regular database cleaning recommended to remove invalid numbers

Time Zone Sensitivity

Recommended Sending Hours: 8:00 AM to 8:00 PM UK time
Avoid sending on UK bank holidays unless urgent
Emergency or security-related messages may be sent outside these hours
Consider different time zones for Scotland, Wales, and Northern Ireland during local holidays

Phone Numbers Options and SMS Sender Types for in United Kingdom

Alphanumeric Sender ID

Operator network capability: Fully supported across all major UK networks
Registration requirements: Pre-registration required for protected sender IDs (especially for banking and financial services)
Sender ID preservation: Yes, displayed as-is on most networks, subject to carrier filtering rules

Long Codes

Domestic vs. International:

Domestic long codes fully supported
International long codes being phased out by UK carriers (complete block from July 2024) Sender ID preservation: Yes, for domestic numbers Provisioning time: 1-2 business days for domestic numbers Use cases: Two-way communication, customer service, transactional messages

Short Codes

Support: Fully supported across all UK carriers Provisioning time: 8-12 weeks for approval and setup Use cases: High-volume marketing, 2FA, emergency alerts, promotional campaigns

Restricted SMS Content, Industries, and Use Cases

Restricted Industries:

Cannabis-related content (strictly prohibited)
Gambling (requires special permissions)
Financial services (requires sender ID pre-registration)
Adult content (heavily restricted)

Content Filtering

Carrier Filtering Rules:

BT/EE implements strict filtering for financial and banking messages
Keywords related to gambling, adult content, or financial scams are monitored
URL shorteners may trigger spam filters

Best Practices to Avoid Blocking:

Use registered sender IDs
Avoid excessive punctuation or all-caps
Limit URL usage in messages
Maintain consistent sending patterns
Use clear, straightforward language

Best Practices for Sending SMS in United Kingdom

Messaging Strategy

Keep messages under 160 characters when possible
Include clear call-to-action
Personalize using recipient's name or relevant details
Maintain consistent brand voice

Sending Frequency and Timing

Maximum 4-5 marketing messages per month per recipient
Respect quiet hours (8 PM - 8 AM)
Consider UK bank holidays and local events
Space out messages to avoid overwhelming recipients

Localization

British English spelling and terminology
Consider regional variations (Scotland, Wales, Northern Ireland)
Support for Welsh language required for services in Wales
Clear date formats (DD/MM/YYYY)

Opt-Out Management

Process STOP requests within 24 hours
Maintain comprehensive suppression lists
Confirm opt-out with one final message
Regular audit of opt-out processes

Testing and Monitoring

Test across all major UK carriers (EE, Vodafone, O2, Three)
Monitor delivery rates by carrier
Track opt-out rates and patterns
Regular testing of opt-out functionality

SMS API integrations for United Kingdom

Twilio

Twilio provides a robust SMS API with comprehensive UK support. Integration requires an account SID and auth token for authentication.

import { Twilio } from 'twilio';

// Initialize Twilio client with environment variables
const client = new Twilio(
  process.env.TWILIO_ACCOUNT_SID,
  process.env.TWILIO_AUTH_TOKEN
);

async function sendUKSMS(
  to: string,
  message: string,
  senderId: string
): Promise<void> {
  try {
    // Ensure UK number format compliance
    const formattedNumber = to.startsWith('+44') ? to : `+44${to.slice(1)}`;
    
    const response = await client.messages.create({
      body: message,
      from: senderId, // Alphanumeric or UK number
      to: formattedNumber,
      // Optional parameters for delivery tracking
      statusCallback: 'https://your-webhook.com/status'
    });
    
    console.log(`Message sent! SID: ${response.sid}`);
  } catch (error) {
    console.error('Error sending message:', error);
    throw error;
  }
}

Sinch

Sinch offers a REST API for SMS with strong UK market support. Authentication uses API tokens and service plan IDs.

import axios from 'axios';

interface SinchSMSResponse {
  id: string;
  status: string;
}

async function sendSinchSMS(
  to: string,
  message: string,
  senderId: string
): Promise<SinchSMSResponse> {
  const SINCH_API_TOKEN = process.env.SINCH_API_TOKEN;
  const SERVICE_PLAN_ID = process.env.SINCH_SERVICE_PLAN_ID;
  
  try {
    const response = await axios.post(
      `https://sms.api.sinch.com/xms/v1/${SERVICE_PLAN_ID}/batches`,
      {
        from: senderId,
        to: [to],
        body: message,
        delivery_report: 'summary'
      },
      {
        headers: {
          'Authorization': `Bearer ${SINCH_API_TOKEN}`,
          'Content-Type': 'application/json'
        }
      }
    );
    
    return response.data;
  } catch (error) {
    console.error('Sinch SMS Error:', error);
    throw error;
  }
}

MessageBird

MessageBird provides a straightforward API for UK SMS messaging with support for various sender ID types.

import { MessageBird } from 'messagebird';

class MessageBirdService {
  private client: MessageBird;
  
  constructor(apiKey: string) {
    this.client = new MessageBird(apiKey);
  }
  
  async sendSMS(
    to: string,
    message: string,
    senderId: string
  ): Promise<any> {
    return new Promise((resolve, reject) => {
      this.client.messages.create({
        originator: senderId,
        recipients: [to],
        body: message,
        // UK-specific parameters
        type: 'sms',
        datacoding: 'plain', // or 'unicode' for special characters
      }, (err, response) => {
        if (err) {
          reject(err);
        } else {
          resolve(response);
        }
      });
    });
  }
}

Plivo

Plivo offers a feature-rich SMS API with strong UK support and detailed delivery reporting.

import plivo from 'plivo';

class PlivoService {
  private client: plivo.Client;
  
  constructor(authId: string, authToken: string) {
    this.client = new plivo.Client(authId, authToken);
  }
  
  async sendSMS(
    to: string,
    message: string,
    senderId: string
  ): Promise<any> {
    try {
      const response = await this.client.messages.create({
        src: senderId, // Must be a valid UK sender ID
        dst: to,
        text: message,
        // UK-specific options
        powerpack_uuid: process.env.PLIVO_POWERPACK_ID, // Optional
        url: 'https://your-webhook.com/delivery-report'
      });
      
      return response;
    } catch (error) {
      console.error('Plivo SMS Error:', error);
      throw error;
    }
  }
}

API Rate Limits and Throughput

Rate Limits by Provider:

Twilio: 100 messages/second (can be increased)
Sinch: 30 messages/second (default)
MessageBird: 60 messages/second
Plivo: 50 messages/second

Throughput Management:

Implement exponential backoff for retry logic
Use message queuing systems (Redis, RabbitMQ)
Batch messages when possible
Monitor throughput metrics

Error Handling and Reporting

Implement comprehensive logging with Winston or similar
Track delivery receipts via webhooks
Monitor common error codes (invalid numbers, network issues)
Set up alerts for unusual error rates

Recap and Additional Resources

Key Takeaways:

Always use proper UK number formatting (+44)
Implement proper opt-out handling
Monitor delivery rates and engagement
Stay compliant with GDPR and PECR regulations

Next Steps:

Review ICO guidelines for SMS marketing
Set up proper consent management systems
Implement robust error handling
Test thoroughly across all major UK carriers

Additional Information: