Spoofed UK mobile numbers are next: caller ID withheld from 15 July 2027

UK phone networks are already blocking on the order of a million scam calls a day, and Ofcom has confirmed the next tranche: international calls that fake a UK mobile number as their caller ID. From 15 July 2027, providers must withhold the caller ID on calls arriving from abroad that appear to come from a UK mobile, unless they can verify the number genuinely belongs to the caller. It closes the last big spoofing loophole — roughly 18 months after fake UK landline numbers were cut off at the border.

Why fraudsters love a UK mobile number

People answer calls that look local and personal. In Ofcom's research, 42% of phone users said they had received a suspicious call in the previous three months (February 2025), and 26% said they were likely to pick up a call from an unrecognised UK mobile number — against just 9% who would answer an international number with an unfamiliar country code. Spoofing a UK mobile is therefore the cheapest way to buy credibility, which is exactly what the guidance change removes.

How the clampdown is stacking up

• 29 January 2025 — providers became required to block calls from abroad that falsely display a UK landline number as caller ID. BT alone reported stopping up to one million calls a day in its first month of voluntary blocking.
• 15 July 2026 — Ofcom confirmed a wider package against mobile messaging scams: volume limits on pay-as-you-go SIMs, blocking of numbers linked to scams, and Know-Your-Customer checks for business messaging senders.
• 15 July 2027 — the mobile call rule lands: UK mobile caller IDs presented from overseas must be withheld unless verified. Ofcom is encouraging providers to implement it sooner.

What legitimate business callers should check

If your outbound calls originate in the UK over a number you own, nothing changes — verified caller ID is the whole point. But it is a good moment to audit what your phone system presents. Presenting a mobile number you do not control, or letting a softphone default to a random presentation number, is how legitimate firms end up looking like fraud. A SIP desk phone or softphone with outbound caller ID control lets you set exactly which number shows, and a real UK virtual number gives you a caller ID that passes any verification check because it is genuinely yours. If your numbers came from a provider you are leaving, porting rules let you take them with you — as we covered in Ofcom's porting rules.

Related: Porting rules mean every business number can be kept · 141 days left: the PSTN countdown