Action Required: UK SMS from International Long Codes Blocked — Compliance Updates for 2023 & 2024

Overview

If you send SMS messages to UK mobile numbers, your deliverability and compliance are at risk unless you update your sender types. Starting June 1, 2023, UK carriers began blocking international long codes for Application-to-Person (A2P) traffic. In 2024, further regulatory requirements have been introduced for UK long codes themselves.

What Changed in 2023

• Carrier Blocking of International Long Codes
  From June 1, 2023, UK network operators started blocking SMS from non-UK long codes. These numbers were originally designed for Person-to-Person (P2P) use, but many businesses were using them for A2P traffic, which carriers now classify as abuse of P2P routes.

• Impact: Any SMS sent to UK recipients from an international long code is likely to fail.
  
  

What’s Changing in 2024

Twilio and UK regulators have layered on stricter compliance requirements:

1. Regulatory Compliance Bundles (RC bundles)

   • From May 27, 2024, all new UK long codes require an approved RC bundle before they can send SMS or make calls.

   • From September 30, 2024, all UK long codes (new or old) must have an approved RC bundle.

2. Know Your Customer (KYC)
   Businesses must provide documentation to verify their identity and intended use case before using UK long codes.

3. Full Enforcement of Blocking
   By mid-2024, all UK carriers had aligned to enforce these rules. Traffic from international long codes is universally blocked, and unregistered UK long codes will also fail.

What You Need to Do

Step 1. Stop Using International Long Codes

• If you are still sending SMS from non-UK numbers to UK recipients, switch immediately.

Step 2. Use Approved Sender Types

• UK Long Code (Local Number) — Requires KYC and regulatory approval.

• Alphanumeric Sender ID — For one-way traffic, brand your sender name (e.g., YourCompany).

• Short Code — For higher-volume or two-way messaging, apply for a UK short code (12–16 weeks provisioning).

Step 3. Register Your Numbers

• Submit your Regulatory Compliance (RC) bundle in Twilio Console.

• Provide the necessary KYC documents (business name, address, use case, etc.).

Step 4. Monitor Message Logs

• In Twilio Console, use Messaging Insights to filter:

  • “From Country ≠ UK” and “To Country = UK” → find non-compliant traffic.

• Look for blocked or undelivered messages and update routing.

How to Buy a UK Number in Twilio

1. Go to: Console → Develop → Phone Numbers → Buy a number

2. Set Country = UK

3. Un-check Voice (if you want SMS-only)

4. Select an SMS-capable number and complete RC bundle submission

Timeline Recap

• June 1, 2023 → UK carriers begin blocking international long codes.

• May 27, 2024 → New UK long codes require RC approval.

• July 30, 2024 → Full carrier enforcement across all networks.

• September 30, 2024 → All UK long codes (new + existing) must have RC approval.
  
  
  

Key Takeaways

• International long codes cannot be used for UK SMS.

• All UK long codes now require KYC and regulatory compliance.

• Alphanumeric Sender IDs and short codes remain valid alternatives.

• Act now to avoid message failures and regulatory issues.