Hiding a number from the person you call doesn't hide it from the phone system. Networks pass the real number between them for billing and regulation, and that record is what makes tracing possible. Whether the police will actually trace a call depends on what the calls are.

When the police get involved

Police can request communications data from networks when investigating crime. Withheld calls that may justify it include:

  • threats of violence;
  • abusive, indecent or menacing calls;
  • repeated calls that form part of harassment or stalking;
  • persistent calls intended to cause annoyance, inconvenience or anxiety, which can be an offence under the Communications Act 2003.

A handful of silent sales calls or spam won't usually meet that bar. For those, reporting to your provider, the ICO or Ofcom is the right route.

What "no caller ID" can mean

"Withheld" or "private" usually means the caller chose to hide the number, for example with 141. "No caller ID" or "unknown" can also mean the number simply wasn't passed on, which often happens with calls from abroad or from some business phone systems. International calls are harder to trace because the records sit with foreign networks.

How to build a case

  1. Keep a log: date, time, duration and what was said. Screenshots of your call history help.
  2. Keep voicemails and any related messages.
  3. Call your provider first. Ask for their nuisance or malicious calls team. They can investigate calls to your line and work with the police.
  4. Report to the police: 101 for non-emergencies, or 999 if you feel in immediate danger. Give them your log and your provider's reference number.

What to expect

The police won't normally tell you the caller's number or identity directly; they use it in their investigation. That can feel unsatisfying, but it's the same protection that stops strangers tracing you. Meanwhile, you can reject withheld calls: see can I find out a withheld number for the settings.

If the calls ask for money or personal details rather than threaten you, they're a fraud matter: report them to Report Fraud, or to Police Scotland on 101 in Scotland.