UK numbers. Ofcom rules.
Operations team that knows both.
UK numbers (type on the pricing page). First UK number lands in a few business days — the current ETA is on the pricing page. Hours, not days, for re-orders.
What you get, in plain terms
VoipTower runs voice on the UK direction for international companies whose work touches the UK market. There is no UK legal entity behind any of the operations served here. They are sales teams, support desks, and verification flows based elsewhere — operations that need a credible UK voice presence without a UK office to back it up.
What this page covers
UK numbers (type on the pricing page; other types on request) and the UK numbering plan they sit in. Ofcom's updated CLI framework and what it actually demands. SIP trunking on G.711 a-law, G.711 μ-law, and G.729. PBX work on 3CX, Asterisk, FreePBX, FreeSWITCH, and Magnus Billing.
Reliability, plainly
Your numbers run on a carrier chosen for that direction, and with clean traffic routes rarely misbehave. Monitoring runs around the clock, and anything that needs attention is handled in the same chat as your engineer and account manager.
Why the UK direction goes through a managed model, not DIY
The UK vendor market is unusually crowded, and a first number arrives in a few business days — the current ETA is on the pricing page. PSTN is being switched off in January 2027, so the whole UK base is in active migration. That combination is why the UK has more SIP vendors selling to small operations than almost any other European country.
The real question is operational ownership
So the question for an international operation is not “can we get a UK number?” It is “who owns the operational work once we have one?” Per-seat phone systems (UCaaS) are built for offices with fixed headcount. API-only platforms hand you the parts and assume an engineer to assemble them. Wholesale carriers are built around procurement cycles. VoipTower: configured to your PBX and supported in the same chat.
VoipTower sits in the gap
Wholesale-grade UK numbers and routes, with the engineering work attached, for high-volume operations without an in-house voice team. Not better than per-seat UK products or API platforms — built for a different shape of operation, on purpose.
Ofcom, the rules in force, and what they mean for traffic
The UK regulator is Ofcom — ofcom.org.uk. The broader regulatory basis is the General Conditions of Entitlement, the binding rules every UK communications provider complies with. The framework was last consolidated in early 2026. For B2B voice, the day-to-day rules are about CLI. They tightened in January 2025.
Ofcom's 2025 CLI rules, in force since 29 January
Providers must block international calls presenting a UK CLI, except in specific legitimate cases. This closed the loophole where calls from outside the UK could spoof UK numbers. There is no UK STIR/SHAKEN mandate yet — that work is on a longer roadmap, dependent on the all-IP transition. But the 2025 rules already do most of what STIR/SHAKEN was designed for: traceable, attributable UK CLI on traffic presenting UK numbers. Inbound traffic needs CLI you have legitimate rights to, and the route has to make that provenance verifiable. Spoofing a UK number from outside now gets the call blocked at the network. CLI through VoipTower is routed only for numbers issued through the platform or ported in with confirmed ownership documentation. Arbitrary caller ID is not accepted. How these rules changed provider selection is covered in UK SIP providers: why CLI compliance decides the shortlist.
PSTN switch-off
Openreach retires the UK PSTN on 31 January 2027, which is why the rest of the market is in heavy SIP-transition mode.
The UK numbering plan, and what each range is for
A short B2B-relevant view of the UK plan — what exists in the country, not a list of what we sell. Number types and the current ETA for each country are on the pricing page; other types on request.
| Type | Range | What it is for |
|---|---|---|
| Geographic | London 020, Manchester 0161, Birmingham 0121, Glasgow 0141, Leeds 0113, Liverpool 0151, Edinburgh 0131, plus other 01 and 02 area codes nationwide | Local presence in a specific city or region. The default for support lines, regional brand presence, and sales operations targeting a city. |
| Non-geographic (local-rate) | 03, plus 0345 and 0370 for corporate use | Nationwide numbers charged to the caller at standard geographic rates — a UK-specific feature without a clean equivalent in some other markets. |
| Freephone | 0800, 0808 | Toll-free for the caller. Standard for inbound support hotlines aimed at consumers. |
The ranges that exist but you will not use: 084x and 087x are premium-rate, much diminished since Ofcom's 2015 reforms, and unsuitable as outbound CLI. 07 is the mobile range, allocated to mobile network operators, not standard for B2B DID provisioning. If a UK mobile number is part of your specific requirement, raise it during onboarding — the answer is more nuanced than yes/no.
Geographic numbers — the 01 and 02 ranges — carry an expectation of presence in the numbering area. The document list for each direction is on the pricing page; KYC reality is its own short section below.
Who else serves the UK SIP market
More credible vendors than any other European market. Several are genuinely good. The honest framing is category fit, not superiority.
Voipfone
The established UK SMB choice. Self-service, transparent published pricing, monthly rolling contracts. If your operation is a small UK office and you are happy configuring your own phone system, Voipfone is on your shortlist. Built for fixed headcount and predictable calling.
Gamma
The UK's largest independent SIP trunking provider. Own UK network, broad UCaaS bundle through Gamma Horizon, Microsoft Teams integration. Sold almost entirely through resellers. A recognised UK brand, a feature-complete platform, transacted through a partner rather than directly with the carrier engineering team.
BT Wholesale
The incumbent's wholesale arm — the WHC programme, BT Cloud Voice SIP. Carrier-grade scale, trusted at the largest end. The cost is the procurement cycle. Weeks to months for activation, multi-year contracts, change requests at committee speed.
Twilio, Telnyx, Bandwidth
Excellent if you have an engineering team and want to build voice features yourself. That “if” is the whole point.
There are also smaller niche UK SIP providers competing on price points below the named players — per-channel rates. VoipTower sits in a category none of those fills well: wholesale-grade UK voice operations on a managed contract, for international companies with real volume and no in-house voice engineering team. Not better than Voipfone or Gamma. Built for a different shape of operation, on purpose.
Three operations on the UK direction
Three different companies. Three different traffic types. Three different ASR pictures. The underlying point is the one the data keeps making across markets: ASR is shaped by call type more than by line quality.
Cold outbound — B2B sales
International B2B sales prospecting on UK numbers. Cold lists, mid-day windows. ACD around 27 seconds, PDD 3.59s. Cold UK ASR above sixty comes from route hygiene: clean originating CLI, no spam-flagged numbers in use, numbers replaced when reputation shifts.
Inbound support — customer service
International support taking inbound calls on UK numbers. Real customer service traffic. ACD 1 minute 24 seconds, PDD 2.57s. The ACD is the honest signal — 84-second average call duration means callers reach someone and have actual conversations. 67% is what good inbound support looks like at scale.
Verification — 2FA, OTP, identity
International company running short verification calls. Calls average 13 seconds, because verification is supposed to be fast. PDD 2.01s. People pick up because they were told to expect the call, and hang up the moment they have what they need. PDD under two seconds matters — a slow verification call is a failed verification call.
Three companies. Three call types. Three answer rates between 60% and 68%. None on the same operational stack, but all on UK numbers routed through VoipTower with the same CLI hygiene model behind them. What a “good UK ASR” looks like depends on what kind of calls you are making and to whom.
What UK numbers cost
Pricing. Current rates for UK numbers — setup, monthly, inbound and outbound per minute — are published on our pricing page — the same rates the order form uses. Engineering, PBX setup and SIP trunk configuration — included; number fees are on the pricing page. See current UK rates
Outbound is billed at two rates, landline and mobile.
Setup, configuration, PBX integration, routing, and support sit inside the contract. No integration retainer, no hourly engineering fee. We have no referral or partner arrangements with PBX, CRM or dialer vendors — recommendations follow technical fit.
On timing: the first UK number takes a few business days from documents to active — the current ETA for the United Kingdom is on the pricing page. After that, re-orders run from pre-allocated stock held for your account — the number typically arrives within 1 to 3 hours of the form, sometimes under an hour, occasionally up to a business day when stock needs replenishment. We keep stock because re-ordering numbers should not be a new project every time.
How the work gets done
On onboarding, we open a group chat in your preferred messenger — Telegram, Microsoft Teams, or WhatsApp. No portal you are required to log into. In that chat sit a support engineer, an account manager, and someone from finance. You add your technical leads and decision-makers. Technical questions, scope changes, invoices — answered in the same place by the person who handles each thing.
Team restructure
A request to restructure a team — extensions, lead permissions, statistics access — handled the same day.
Route quality on UK numbers
Checked live in the chat, diagnosed, and put right when the cause sits with us — and kept in the same conversation until it is resolved either way.
Spam score flagged
A spam score climbing on a number — we monitor number reputation and recommend a replacement when a number starts to be flagged; you choose the timing, we execute the swap.
Built around your accounting
Bank transfer (SWIFT, USD) or USDT (TRC20, ERC20, BEP20). A proforma invoice is issued before each top-up; a monthly invoice follows by the 5th of the next month. The flexibility model is the same here as in other markets — billing details settle during onboarding alongside everything else.
Most cases never leave the chat. The cases that make the difference are not dramatic — they are the routine ones handled in the same chat by the right person, in the channel your team already uses.
Documents to get a UK number live
Standard company KYC — company registration, director ID and use case — is done once for your company. Directions with a Local document scope also need proof of a local address. The document list for each direction is on the pricing page.
What is not required
UK incorporation, a UK director, a UK registered office, or any UK-presence proof. International companies can order UK numbers without any UK legal entity. The documents above are standard company KYC, not UK-presence proof. Worth saying plainly because several UK-facing vendors demand local presence proof for local numbers, and a lot of international operations assume the requirement is real for everyone. It is not.
The real check is the use case
Compliance review happens before provisioning, against the use case you state at onboarding.
Which operations this fits
The three case patterns above are the shape of the work on the UK direction. What ties them together: real call volume on the UK direction, no in-house voice engineer, and the conclusion that voice operations should not become a second product the team is building.
Outbound prospecting
Running outbound prospecting at volume, where local UK presence and clean CLI decide whether the call connects.
Customer service on UK numbers
Taking inbound on UK numbers, where answer rate and call duration both matter.
Service verification (2FA, OTP)
Short, fast, reliable calls in high volume — identity checks, one-time passwords, voice 2FA.
If you have real call volume on the UK direction and nobody on staff whose job is route hygiene, the managed model adds up. With your own voice team and enterprise-scale traffic, you will likely build cheaper in-house — a reasonable call, not one we will argue against.
Frequently asked questions
Eight common questions from companies setting up voice on the UK direction.
Is VoipTower a UK company, and do you have UK-registered clients?
No to the first; no to the second. VoipTower has no clients registered as UK legal entities. The companies running UK numbers through us are international operations that need credible UK voice presence without the overhead of UK incorporation. The page proves capability on the UK direction, not a UK client roster.
Do I need to be a UK company to get a UK number through VoipTower?
No. A UK number does not require a UK company, director, address or any UK-presence proof. Standard company KYC — company registration, director ID and use case — is done once for your company. Directions with a Local document scope also need proof of a local address. The document list for each direction is on the pricing page.
How does VoipTower handle CLI compliance under Ofcom's 2025 rules?
CLI is routed only for numbers issued through VoipTower or ported in with confirmed ownership documentation. Arbitrary caller ID is not accepted. This aligns with Ofcom's updated CLI rules, in force since January 2025, which require providers to block international calls presenting a UK CLI from sources that cannot verify legitimate use.
How long until a UK number is live?
Three separate timelines. Your request is reviewed within about 24 hours — KYC and business-case review. The first number in a new country takes a few business days; the current ETA per country is on the pricing page. Re-orders in a country you already operate in run from about an hour, up to 1 business day, from your allocated stock, with no repeat KYC.
What does a UK number cost?
No engineering or integration fees, no per-hour billing; each number has a setup and monthly fee, listed on the pricing page. Current rates — setup, monthly, inbound and outbound per minute — are published on our pricing page — the same rates the order form uses.
Which PBX systems and codecs do you support?
3CX, Asterisk, FreePBX, FreeSWITCH, Magnus Billing, plus standards-compliant auto-dialer platforms. Connection by IP-to-IP or SIP credentials. G.711 a-law, G.711 μ-law, G.729.
How is VoipTower different from other UK SIP providers?
Wholesale carriers sell UK SIP mostly through partner channels, and per-seat phone systems (UCaaS) are built for self-service offices. VoipTower is built for international companies routing to the UK: high-volume B2B operations that want direct contact with the engineering team running the routes.
What about the PSTN switch-off in January 2027?
UK SIP infrastructure is what replaces PSTN. For an international company routing inbound or outbound on UK SIP, this changes nothing about how the service operates.
For technical questions beyond UK scope, see the full FAQ. For services on the UK direction: DID, SIP trunking, PBX setup & CRM connection. For the full country list, the coverage hub. Germany works the same way operationally — see /countries/germany/. Pricing logic and the wider model are on the homepage. Onboarding starts at legal.voiptower.company.
Other priority countries
Many businesses use UK numbers as part of a wider international voice setup. VoipTower covers 25+ countries — with dedicated priority coverage in seven other markets used by call centers, sales teams, e-commerce, and logistics operations.
Germany 🇩🇪
German geographic DID; other types on request. SIP trunking, German-language support routing.
Germany coverage →France 🇫🇷
French DID numbers, SIP trunking, support routing for France.
France coverage →Canada 🇨🇦
Canadian DID numbers, sales and support workflows.
Canada coverage →Poland 🇵🇱
Polish DID numbers, SIP trunking, call center and support routing.
Poland coverage →Czech Republic 🇨🇿
Czech DID numbers, business VoIP infrastructure, PBX setup and CRM connection.
Czech Republic coverage →South Africa 🇿🇦
South African DID numbers, SIP trunking, support routing for South Africa.
South Africa coverage →Argentina 🇦🇷
Argentine DID numbers, sales and support workflows.
Argentina coverage →Talk to the people who would run it
If the UK is a direction you are sizing, the useful next step is a conversation with the engineers who would actually configure it — not a sales script. Bring your volume, your PBX, your timeline. We will tell you plainly whether the UK direction through VoipTower fits what you are doing.