Europe
SIP Trunk United Kingdom — +44 Termination & DID Numbers
Ofcom requires every call into the UK to carry a valid, dialable caller ID, and UK networks now block calls that present malformed or unallocated numbers. If your CLI fails those checks the call never rings, so getting it right comes before price.
Overview
Routing calls to United Kingdom
Most United Kingdom traffic we see ends in London, Manchester and Birmingham, Glasgow, Leeds and Bristol. Each +44 prefix is mapped to at least two carriers, and we watch ASR, ACD and PDD per prefix so a degrading route is replaced before your agents notice.
Ofcom sets the United Kingdom numbering plan, and our prefix tables follow it closely. Supported number types: geographic, national, mobile and toll-free. Inside the country, numbers are dialled with a 0 trunk prefix. Strip it before you send the call, and send 44 followed by the national number.
Outbound termination to United Kingdom starts as soon as your balance is topped up. Local DIDs are different: Ofcom rules usually require address and identity documents, which our team collects and checks before activation.
What you get
What you get in United Kingdom
One account and one balance, with the same SBCs for termination and inbound numbers.
CLI route tier
Caller ID delivered end to end on +44 calls. Use it for sales, support and any traffic where answer rates matter.Non-CLI route tier
A lower-cost tier where caller ID delivery is not guaranteed. Suitable for internal or transactional traffic that does not depend on the CLI.Number types
Geographic, National, Mobile, Toll-free. DID availability varies by range and city.Codecs
G.711a/u and G.729 on every route, G.722 and Opus where the far end supports them. T.38 for fax.Channels on demand
Concurrent call limits are set per account and raised as your traffic grows. No fixed channel bundles.Multi-carrier failover
Every +44 prefix is mapped to more than one carrier. Failed attempts move to the next one automatically.
Number formats
How to dial United Kingdom from your PBX
Send E.164 digits. The sample number below shows the format only.
| Format | Example | Notes |
|---|---|---|
| International (E.164) | +44 20 7946 0018 | How the number is written and stored. |
| Sent from your PBX | 442079460018 | E.164 digits with no plus, prefixed by your tech prefix if your account uses one. |
| With 00 exit code | 00 44 20 7946 0018 | Accepted on the trunk. We normalise it to E.164. |
| National format | 020 7946 0018 | Dialled inside United Kingdom. Strip the trunk prefix before sending. |
Compliance
United Kingdom rules to know
What applies before your first call or your first DID goes live.
Compliance box
- Regulator
- Ofcom
- Caller ID
- A valid CLI that you are entitled to use is required on CLI routes. Spoofed or unallocated numbers are blocked.
- DID KYC
- Usually required
- Note
- Ofcom CLI rules: the caller ID must be valid, dialable and one you are entitled to use. Invalid CLIs are blocked.
- Note
- Ranges: 01/02 geographic, 03 non-geographic (charged as geographic), 07 mobile, 080 freephone.
Rules change — our team confirms current requirements before activation.
Spam, robocalls and fraud are not allowed. Read our acceptable use policy.
Use cases
Who uses United Kingdom routes
- 01
Contact centres presenting 01/02 geographic or 03 non-geographic CLIs to UK consumers
- 02
Businesses replacing ISDN30 and PSTN lines ahead of the BT switch-off
- 03
0800 and 0808 freephone numbers for nationwide customer service
Setup
Start calling United Kingdom in 3 steps
- 01
Top up $200
Open a prepaid account and add balance by USDT (TRC20), BTC or card. - 02
Add your trunk
Whitelist your PBX IP or create digest credentials, then point your outbound route at our SBC. - 03
Dial +44
Send 44 + national number in E.164 and check the CDR for your first test call.
Further reading: SIP Trunk UK: Number Ranges, CLI and Setup
FAQ
United Kingdom SIP trunk questions
What CLI can I present on UK calls?
A valid, dialable UK or international number that you are entitled to use and that can be called back. Ofcom's guidance bans presenting numbers you don't hold or that are not in use.
What is the difference between 01/02 and 03 numbers?
01 and 02 are geographic numbers tied to an area code. 03 numbers are non-geographic but are charged at geographic rates to callers, which makes them popular for national service lines.
Do UK DIDs need proof of address?
Usually yes for geographic ranges. Expect a UK address in the area or a business address, plus company details.
How do I dial UK numbers through the trunk?
Drop the leading 0 and send 44 + number, for example 442079460018 for a London number.
