What is number porting? (and why do you need to know about it…)

What is number porting?

Number porting is the process of moving an existing phone number from one communications provider to another, without changing the number that your customers dial. Ofcom describes it as a regulated facility that lets subscribers change provider while keeping their existing telephone number.

In practice, that means if you are switching from one provider to another and you want to keep your main business number, you ask your new provider to port the number across. They work with your old provider in the background so that, after an agreed date, calls to that number route to your new service instead.

Number porting can apply to:

• geographic landline numbers (for example, 0203, 0161, 029)
• non-geographic numbers such as 03, 08 or 09 ranges
• VoIP or cloud-based business numbers
• mobile numbers, using a slightly different process

Why number porting matters for UK businesses in 2025

Number porting has always been useful, but it is becoming critical for UK businesses because of three big shifts.

1. The BT landline switch off and move to digital voice

BT is switching off the old PSTN and ISDN analogue landline network by January 2027, with many business customers urged to migrate earlier to avoid issues on ageing infrastructure. All landline services will move to all IP digital solutions, such as VoIP or hosted PBX systems.

For businesses that want to keep the numbers customers already know, number porting is the bridge from traditional lines to modern cloud phone systems.

2. Customers trust the numbers they already recognise

Your phone number appears everywhere, from Google Business listings to invoices. Asking customers to update their records every time you change provider is slow, risky and easy to get wrong. Porting lets you upgrade your phone system or call answering without erasing that hard-earned familiarity.

3. Competition between providers is stronger than ever

Ofcom’s portability rules are designed to support competition, so you can switch to a provider that offers better support, features or pricing without losing your number. For businesses using outsourced receptionists or AI voice services, number porting protects your flexibility and bargaining power.

How the number porting process works

Behind the scenes, number porting involves both communications providers (CPs) and the network operators (NOs) that carry calls on their behalf. You do not need to be a telecoms expert, but it helps to understand the basics.

Step 1: choose your new provider

First, pick the provider you want to move to. This might be a VoIP platform, a unified communications provider or a specialist telephone answering service such as Moneypenny. Confirm that they can accept ports for your type of number (for example, 01/02 geographic, 03, 08 or international).

Step 2: request a port and provide details

Your new provider will ask for information about your existing line so they can submit a porting request. This usually includes:

• the number or range of numbers you want to port
• the current provider’s name
• the account name, billing address and account number as they appear on your bill
• authorisation on headed paper or via a formal letter of authority from your business

Step 3: providers agree the porting date

Your new provider will send a formal porting request to your existing provider. If there is a porting agreement in place between their underlying networks, they will agree a transfer date. Where an agreement is not yet in place, this can add time while an appropriate technical route is set up.

Step 4: the number moves across

On the agreed date, your number will be switched from the losing provider to the gaining provider. In most cases, any downtime is very short, often a few minutes, and many ports complete without customers noticing at all. Once complete, all future calls route to your new service.

How long number porting takes and what it costs

The time it takes to port a number depends on the type of number, how many numbers are involved and how clean your account data is.

• Single business landline or VoIP number: often around 10–14 working days from a valid request, sometimes quicker.
• Large ranges or complex setups: multi-line ISDN, DDI ranges and multi-site ports can take longer and may need extra checks.
• International numbers: timelines vary by country and local regulation.

Some providers charge an administration fee per number or per range. Others include a certain level of porting in their setup costs. You may also need to pay any early termination fees owed to your current provider if you are leaving before your contract ends. Guides from telecom providers and messaging platforms recommend reviewing your current contract and any porting charges before you start the process.

Mobile number porting and the text to switch rules

Mobile number porting follows a slightly different process, although the principle is the same: you can keep your mobile number when you switch network.

Since 2019, Ofcom’s text to switch rules allow you to get a Porting Authorisation Code (PAC) by text, without having to call your existing provider. To keep your number when you move network, you simply text PAC to 65075. Your provider must reply by text, normally within a minute, with your PAC and any important information about early termination charges.

You then give that PAC to your new mobile network, who arrange the transfer. Once the port completes, your old SIM will stop working and your new SIM will take over with the same number.

Number porting vs getting a new number: pros and cons

Porting your number is often the best option for continuity, but there are times when choosing a new number can make sense. Many expert guides recommend reviewing both routes before you decide.

Benefits of porting your existing number

• no need to reprint signage, stationery or vehicle branding
• less risk of customers calling the wrong number or thinking you have closed
• better continuity across Google Business listings and online directories
• easier for long standing customers to recognise and trust your brand

When a new number can be useful

• you want a more memorable or location-specific number to support growth
• you are changing business model or region and want a clean break
• your existing number is heavily targeted by spam or has been misused in the past

Some businesses choose a hybrid approach: they port their existing main number for continuity, then add new regional, national or freephone numbers for campaigns, tracking or specialist teams.

Common number porting problems and how to avoid delays

Most ports run smoothly, but there are a few common issues that can delay or block a port if they are not addressed up front. Other providers and telecom experts highlight similar themes in their porting guides.

1. Mismatched account details

If the details on your porting request do not exactly match the details on your current provider’s records, the port can be rejected. Always check the latest bill and confirm the official account name, address and account number before you submit anything.

2. Active services on the line

Certain added services, such as broadband or alarm lines, can complicate a port. Your new provider may advise on whether these need to be moved, cancelled or separated before the port goes ahead.

3. Contract or minimum term issues

If you are still inside a minimum term, you may face early termination charges from your existing provider. That does not usually stop the port (you have a regulated right to port in most cases), but you should go in with your eyes open about any costs.

4. Complex number ranges or international ports

Large ranges, international numbers or very old allocations sometimes take longer to move. Building extra time into your project plan is wise if your setup is more complicated than a single number at a single site.

5. Lack of a clear backup plan

Although downtime is usually minimal, it makes sense to have a backup. For example, you can arrange temporary call forwarding or have a secondary number ready that can be shared with key clients in the unlikely event of a longer outage.

How Moneypenny supports number porting and clever numbers

At Moneypenny, number porting is a familiar part of onboarding. We know how important it is to keep the number customers already know, while upgrading the way calls are answered.

When you move your call answering to us, we will:

• check whether our providers already have porting agreements in place with your existing carrier
• guide you through the letter of authority and account detail requirements
• coordinate the porting date to minimise disruption to your team
• route calls to our receptionists, AI Voice or your own team according to your preferences

If you decide you would rather start afresh, our business telephone number service lets you choose from a wide range of regional, national and freephone numbers, set up in minutes and routed anywhere you choose. For many SMEs, the ideal mix is keeping their main published number through porting, and adding new numbers for campaigns, tracking or new regions.

Number porting FAQs for UK businesses

Number porting can look technical on paper, but most of the hard work sits between the providers. With the right partner, you can keep the number your customers trust while gaining the flexibility, resilience and service quality your business needs for the next phase of growth.