Answer rates live and die on the number at the top of the screen. Show the wrong one and the call is ignored; show one you are not entitled to and, increasingly, it never arrives at all.
Every UK call carries two numbers
A UK call carries two pieces of caller ID, and it helps to keep them apart:
- The network number is set by the network the call starts on and identifies the line it came from. It is used for tracing and is not normally what people see.
- The presentation number is the one displayed on the phone you are calling. This is the one you choose — within rules.
Choosing your presentation number is legitimate and normal. A business with forty agents does not want forty different numbers on customers’ screens; it wants one, the one on its website. The rules exist to stop that freedom being used to show a number that is not yours.
The rules for the number you present
Ofcom’s guidance on calling line identification comes down to four tests. The number must be:
- Valid and dialable — a real UK number, in a range that is in use, that can be rung back.
- Yours to use — you hold it, or the organisation you are calling on behalf of has authorised you to use theirs.
- Answered by you — ringing it back reaches you or someone acting for you, not a dead line or another company.
- Not premium rate — nobody should have to pay extra to return a missed call.
Networks are expected to block calls whose caller ID fails the first test outright. A number that is badly formatted, not in use, or not dialable often does not get through at all — it simply fails, and from your side it looks like a poor answer rate.
Calls from abroad showing a UK number
This is the change most offshore teams have run into. UK networks now block calls arriving from abroad that display a UK landline number, apart from a limited set of legitimate cases. The rule targets scammers, but it catches anyone who simply sets a UK number on calls sent into the UK over an international route.
UK mobile numbers were left out at first, so that people roaming abroad could still show their own. In 2026 Ofcom finalised guidance closing that gap too: providers should withhold the caller ID on calls that appear to come from a UK mobile roaming abroad unless they can verify it is genuine. In practice, a 07 number shown on offshore traffic should be expected to arrive as withheld.
Ask how your calls enter the UK networkWhether your presentation number survives depends on the route your calls take into the UK and whether the provider handing them over can vouch for the number. It is the single most useful question to ask a provider if your agents are outside the UK.
Choosing the number
- 01 and 02 geographic numbers look local, and a local-looking number gets answered more often. Good for regional campaigns, provided the number is genuinely one you hold.
- 03 numbers cost the same to call as a geographic number, from landlines and mobiles, and read as an organisation rather than a person. A sound default for a brand.
- 0800 and 0808 are free to call back from UK landlines and mobiles. They encourage call-backs, and you pay for every one.
- 07 mobile numbers are tempting because people answer mobiles. They are also the most scrutinised range for spoofing. Use one only if it is a real mobile you hold, and not on traffic from abroad.
When a valid number still goes unanswered
Phones and call-screening apps now label numbers using signals the caller never sees: how many calls a number makes, how short they are, how often they are rejected, and how often people report them. A number that dials thousands of short calls a day and is never rung back will be labelled however valid it is.
The answer is not to cycle through fresh numbers to stay ahead of the labels. Networks and regulators read number rotation as a sign of someone hiding, and it destroys call-backs, which are often the best leads a campaign produces. What works is duller: a stable number per campaign, somebody answering when people ring it, sensible volumes per number, and clean, screened lists — see the UK outbound calling rules.
How this differs from the US
US carriers sign calls cryptographically and label what they cannot verify — there is a full explanation of STIR/SHAKEN here. The UK has no equivalent signing system yet. It relies on rules about which numbers may be presented, and on networks blocking calls that break them.
UK numbers you hold outright — the right kind of number to present.
See UK DIDs
