- Ofcom administers the UK numbering plan and the rules that allow customers to keep their number when switching provider, known as number portability.
- Geographic numbers beginning 01 and 02, and non-geographic 03 numbers, can generally be ported to a hosted VoIP platform.
- Many 08 numbers, including 0800 and 0845, can usually be moved to a VoIP provider, though arrangements depend on the originating and receiving providers.
- Porting is requested through the new (gaining) provider, who coordinates the move with the existing (losing) provider.
- The analogue network is being withdrawn under the all-IP migration Openreach expects to complete in 2027, making the move of numbers onto IP-based services increasingly routine.
Most UK business numbers, including 01, 02, 03 and many 08 numbers, can be ported to a hosted VoIP platform through your new provider; some special and shared-cost numbers may have restrictions.
Last reviewed: June 2026
How number portability works in the UK
Number portability is the arrangement that lets a customer keep an existing telephone number when moving to a different provider. Ofcom administers the UK numbering plan and sets the rules that underpin this, so a business does not have to give up a number it has advertised for years simply because it is changing the underlying service. When moving to VoIP, the number is not recreated; the same number is transferred so callers reach the business exactly as before.
The mechanism behind portability is routing rather than reassignment. A ported number keeps its original number range, which is held in the records of the provider that was first allocated that block by Ofcom, but a routing instruction is added so that calls to it are handed off to whichever network now serves the customer. This is why a number can move repeatedly between providers over its life without ever changing the digits a customer dials. It also explains why both the gaining and losing providers have to act together: the losing provider releases the number for porting and the gaining provider accepts responsibility for delivering calls to it.
This matters most for organisations whose number is part of their identity, printed on vehicles, signage and stationery. As the analogue network retires under the all-IP migration Openreach expects to complete in 2027, moving numbers onto IP-based hosted platforms is becoming the normal route. Understanding which numbers can move, and how, removes much of the anxiety around the switch, and lets a business treat the change as a planned project rather than a forced disruption.
Which numbers can be ported to VoIP
The numbers most businesses care about are geographic numbers, which begin 01 or 02 and are tied to an area, such as 020 for London or 0161 for Manchester. These can generally be ported to a hosted VoIP platform, and a key benefit of VoIP is that the number is no longer physically anchored to the premises, so it can follow the business if it relocates within the same area arrangement. Non-geographic 03 numbers, which Ofcom requires to be charged at the same rate as 01 and 02 calls and which cannot carry a revenue share, can also typically be ported.
A point worth understanding about geographic numbers is the link to the dialling area. Under the numbering plan the 01 or 02 prefix signals a geographic region, and providers have historically expected the served address to sit within that area. Because a VoIP number is delivered by routing rather than by a physical copper pair, a business can in practice answer its London 020 number from anywhere with an internet connection, which is one of the features that makes VoIP attractive to organisations with home or hybrid workers. The number itself still belongs to the geographic range, so it continues to signal the original locality to anyone who reads it.
Many 08 numbers can move too. Freephone 0800 numbers and shared-cost numbers such as 0845 are commonly portable to a VoIP provider, though the practical arrangements depend on the originating and receiving providers and on how the number is currently hosted. Because these number ranges have their own billing and routing characteristics, with some carrying a service charge that is set and declared separately, it is worth confirming the specifics with the gaining provider rather than assuming a single rule covers all 08 numbers.
Number portability to VoIP by number type
The table below summarises the common position by number type. It is a general guide; the gaining provider confirms what is possible for a specific number, since hosting and contractual factors can vary.
| Number type | Example | Portable to VoIP |
|---|---|---|
| Geographic | 020, 0161, 0117 | Generally yes |
| Non-geographic 03 | 0300, 0345 | Generally yes |
| Freephone | 0800, 0808 | Usually, provider dependent |
| Shared cost | 0845, 0844 | Usually, provider dependent |
| Mobile | 07xxx | Not to a fixed VoIP service |
Numbers that may not port and what to check
Not every number moves cleanly to a fixed VoIP service. Mobile numbers in the 07 range belong to mobile networks and are not ported onto a hosted fixed VoIP platform in the way a landline number is, though a business may keep them separately on a mobile service and use the porting authorisation code process that applies to mobiles. Premium rate numbers and certain special-arrangement numbers can carry restrictions tied to how they are hosted and billed, so they need to be checked individually rather than assumed portable.
There are also practical conditions that apply to any port. The number must usually be active and not in the middle of another change, the account details given to the gaining provider must match the records held by the losing provider, and any outstanding contractual issues on the old account can hold up a move. A frequent cause of delay is a simple mismatch between the business name or address as the losing provider has it recorded and the details the customer supplies to the gaining provider, so checking the most recent bill for the exact account particulars before submitting a request saves time. The safest approach is to give the gaining provider the full list of numbers early, so any that need special handling are identified before a cutover date is fixed.
How the porting process works
Porting always starts with the gaining provider, the one the business is moving to. The customer supplies the numbers to be ported and the account details for the existing service, and the gaining provider submits the request to the losing provider. The two providers coordinate the transfer and agree a date and time for the cutover. Throughout this period the existing service continues to work, so there is no need to disconnect early.
A critical point is not to cancel the old line or service before the port completes, because cancelling first can release the number and cause it to be lost. Once a number is given up rather than ported, it returns to the pool held by the original range holder and may not be recoverable, so the sequence of events matters as much as the request itself. On the agreed cutover, calls to the number begin routing to the new VoIP platform. Any brief interruption is usually confined to the switchover window itself. Once live, the business should test inbound calls from both a landline and a mobile to confirm the number rings through to the new system as expected before relying on it fully.
What changes once a number is on VoIP
Once a number sits on a hosted VoIP platform, the way calls are handled changes even though the number itself is unchanged. Inbound calls are delivered over the internet connection to the provider's platform and then routed to whichever devices or apps the business has registered, which can include desk handsets, softphones on laptops and mobile applications. This decoupling of the number from a single physical socket is the practical reason organisations move: one advertised number can ring several people in several locations, follow staff who work from home, and divert automatically out of hours without any change to the digits a customer dials.
The change also brings responsibilities that did not apply on the old copper line. Because the service now depends on a broadband connection and on mains power for the router and handsets, a business should consider resilience for a power cut or an internet outage, for example by routing unanswered calls to a mobile. Call quality depends on the connection carrying the voice traffic, so a congested or unreliable line can affect a ported number in ways a copper line never did. These are configuration matters rather than barriers to porting, but planning for them at the point of migration keeps the experience for callers seamless after the number has moved.
Frequently Asked Questions
Can I port my 01 number to VoIP?
In most cases yes. Geographic numbers beginning 01 or 02 can generally be ported to a hosted VoIP platform under Ofcom number portability arrangements. A benefit is that once on VoIP the number is no longer tied to the physical premises in the same way, so it can move with the business and be answered from any location with an internet connection. The gaining provider confirms the details for your specific number.
Can I port an 0800 number to VoIP?
Usually yes. Freephone 0800 numbers can commonly be moved to a VoIP provider, although the arrangements depend on the originating and receiving providers and on how the number is currently hosted. Because 08 ranges have their own routing and billing characteristics, with some carrying a separately declared service charge, it is worth confirming the specifics with the gaining provider rather than assuming.
How do I port my number to a VoIP provider?
You start with the new (gaining) provider, supplying the numbers to be ported and the account details for your existing service exactly as they appear on your latest bill. The gaining provider submits the request to your current provider, and the two coordinate a cutover date. Do not cancel the old service first, as cancelling can cause the number to be lost rather than ported.
How long does porting to VoIP take?
It varies with the number type, the providers involved and whether any account details need correcting, so a fixed duration cannot be promised. Geographic numbers often move more straightforwardly than some special-arrangement numbers, and a detail mismatch between the two providers' records is a common cause of delay. Giving the gaining provider the full list of numbers early helps any that need special handling to be identified before a date is fixed.
What happens to my number during the porting process?
Your existing service keeps working throughout the porting period, so there is no gap while the request is processed. On the agreed cutover, calls begin routing to the new VoIP platform, with any brief interruption normally confined to the switchover window. After go-live, test inbound calls from both a landline and a mobile to confirm the number rings through correctly before relying on it.
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