📞 VoIP Caller Presentation for Emergency Services (999/112)

How Caller ID and Location Information Work in the UK

When you dial 999 or 112 from a VoIP service, the emergency operator must be able to identify who is calling and where the caller is located. Caller Line Identification (CLI) is a key part of this process, and the rules for VoIP differ from traditional landlines.

This guide explains how caller presentation works, why it matters, and what customers and admins must do to ensure emergency calls route correctly.

🔍 What Is Caller Line Identification (CLI)?

Caller Line Identification (CLI) is the telephone number that appears to the emergency operator when a 999/112 call is placed.
Ofcom requires that any CLI sent must be a valid, dialable number that uniquely identifies the caller and can be used to call them back.
Correct CLI presentation ensures that the call is routed through the emergency network and that responders can identify the caller if the line drops. [ofcom.org.uk]

🏠 Registered Address and Location Information

Unlike mobile networks, VoIP services do not automatically detect the caller’s location.
Emergency operators rely on the registered address linked to the CLI being presented. If this address is missing or outdated, the operator may not be able to determine your location.

VoIP providers state that callers must keep their emergency address updated, as using the service at a different location can cause incorrect routing.

Many providers also verify the submitted address before enabling emergency calling. 

☎️ How Caller Presentation Works for VoIP Emergency Calls

✔ The CLI must be:

• A valid UK telephone number.
• A number assigned to your SIP trunk, where possible.
• A number for which the customer has supplied a verified emergency address.

This enables emergency operators to:

• Identify and call back the number.
• Retrieve the correct registered address.
• Route the call to the nearest emergency handling authority. [ofcom.org.uk]

✔ Emergency calls must not include “+44”

Most UK carriers require the +44 prefix to be removed from CLI for emergency calls so that calls route correctly within BT’s 999 network. This behaviour is standard across UK VoIP networks and is often implemented by carriers as a manual configuration change.

✔ CLI withholding does not apply

Even if you normally withhold your number, CLI cannot be suppressed for 999/112 calls. Emergency calls override privacy settings to ensure a valid number is delivered.

⚠️ Why CLI Matters for Emergency Response

Sending an invalid or anonymous number may result in:

• No automatic address lookup
• Delayed response
• Difficulty calling the user back
• Incorrect routing if the CLI does not match a registered address

🛠 Customer Responsibilities

To ensure emergency calls route correctly, customers must:

✔ Provide accurate information

• Supply the correct registered address for each number assigned to the VoIP service.
• Keep address information updated if the service location changes. 
• Sign and return the Emergency Services Disclaimer form, which confirms understanding of the contents of this article

✔ Use a valid, assigned presentation number

The number shown to emergency services should be:

• Part of your SIP trunk
• Associated with a registered and verified address

✔ Train staff

Callers must be prepared to verbally confirm:

• Their location
• Their phone number

because the VoIP location is not automatically detected.

✔ Maintain alternative access

VoIP can fail during:

• Power outages
• Broadband failures
• Equipment faults

Providers recommend keeping a mobile phone available as a backup. 

📝 Summary

VoIP emergency calls rely on:

• A valid, dialable CLI
• A correct, verified registered address
• Proper SIP trunk and dial‑plan configuration
• Accurate data provided by the customer

Without a correct caller presentation, emergency services may not be able to locate or call back the caller.