Consultation: Calling Line Identification (CLI) authentication – a potential approach to detecting and blocking spoofed numbers

Published: 28 April 2023
Consultation closes: 23 June 2023
Status: Closed (pending statement)

In this consultation, we are inviting stakeholders’ views on our initial thinking about how Calling Line Identification (CLI) authentication might work in the UK and the extent to which actions providers are already taking are likely to address the problem of number spoofing. We are not making any proposals for specific regulatory interventions at this stage.

If our provisional view following this consultation is that there is a case for requiring the implementation of CLI authentication, we will publish a full assessment of the likely impact and our proposals for the regulatory rules that would be needed.

Background information

In 2021, Ofcom commissioned a report into the potential challenges of introducing CLI authentication in the UK. The report's insights and recommendations are based on lessons from the implementation of STIR/SHAKEN in the US and Canada, as well as conversations with relevant experts in the UK.

The report provided an early framework to guide our consultation approach, but we recognise (and have taken account of) more recent developments in CLI authentication – in the US and elsewhere. We have published a copy of the report alongside our consultation.


Contact information

CLI authentication team
Riverside House
2A Southwark Bridge Road
London SE1 9HA
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