UK Regulator Cracks Down on CLI Spoofing with New Numbering Rules

Ofcom has announced a fresh set of rules to combat caller ID (CLI) spoofing and nuisance calls, requiring UK telecom providers to verify the authenticity of all outbound numbers before they reach end users.

From October 2025, operators must block any call presenting an invalid, unallocated, or non-E.164-compliant number. The move follows a surge in scams using falsified UK landline or mobile numbers to gain victims’ trust.

Ofcom’s Director of Telecom Security, Helen Carter, said: “These changes will cut off one of the scammers’ favourite tricks—pretending to be someone they’re not. By ensuring only valid, allocated numbers appear on caller ID, we’re making the phone network a safer place.”

Industry groups have welcomed the decision, noting that the alignment with global STIR/SHAKEN standards will make cross-border fraud prevention more effective and protect consumer confidence in voice services.