The UK is gradually switching off its old copper phone network, and by 31 January 2027, traditional PSTN and ISDN lines are due to disappear completely. That change reaches well beyond a single office handset. Many alarm lines, lift phones, fax machines, and card payment terminals still run over those legacy connections and will be affected when they are withdrawn.
If your organisation still depends on any of these services, understanding the BT landline switchover 2027 and the ISDN switch off UK is essential to avoid a last minute scramble.
Planning now gives you the space to pick suitable digital options typically VoIP or other IP‑based systems instead of rushing into whatever is available, and independent VoIP guides are a good place to start comparing routes. From there, the key is to get clear on exactly what is changing and what that means for how your teams, customers and sites communicate every day.
Briefly: The Big Switch Off 2027
The Big Switch Off is the UK‑wide plan to retire all PSTN (Public Switched Telephone Network) and ISDN (Integrated Services Digital Network) services by 31 January 2027, moving everything to digital, IP‑based alternatives. These copper lines have carried business calls for decades, but they were designed for simple voice traffic, not today’s cloud apps, video meetings and remote work. Maintaining the ageing copper network is now costly and less reliable than fibre and IP services, so providers are standardising on digital landlines and VoIP to support modern communication.
PSTN Switch off Alert : Countdown Begins Now !
Any organisation still using copper‑based lines should assume it is affected, with the biggest impact on businesses relying on traditional landlines or older PBX systems connected via PSTN or ISDN. Small offices with a single analogue line, call centres on legacy PBX platforms and sites where key functions still run over fixed PSTN connections are especially exposed.
Devices and services likely to stop working if not migrated:
Businesses that leave these services on copper until the last moment risk sudden failures and rushed, expensive emergency migrations instead of a controlled, phased transition.
Stop‑sell: New PSTN/ISDN services are already in “stop‑sell” across most exchanges, so you cannot order new analogue or ISDN lines.
Full shutdown: By 31 January 2027, remaining PSTN and ISDN lines will be switched off and will no longer carry calls.
What replaces them: Businesses must move to VoIP, SIP trunks or other cloud‑based IP voice services to keep numbers and phone‑based systems working.
Understanding the key dates for the UK’s PSTN and ISDN retirement is essential for businesses. Early preparation is the difference between a smooth transition and operational chaos.
Phase / Date | What Happens | What Businesses Should Do |
Stop‑Sell (from Sep 2023) | New PSTN/ISDN lines are no longer sold in most UK exchanges. | Stop planning any new analogue lines. Look at digital options. |
Migration Window (2025–2026) | Best time to move services from PSTN/ISDN to VoIP or other IP systems. | Audit lines, test VoIP, train staff, and migrate in stages. |
Final Shutdown (31 Jan 2027) | All remaining PSTN/ISDN lines are turned off and stop working. | All services must be moved before this date to avoid outages |
Starting your migration before December 2025 ensures enough buffer time to address unexpected issues, train your team, and avoid the costly rush in early 2027. Businesses that delay risk emergency migration costs, service outages, and operational disruption on the hard deadline of 31 January 2027.
Switch Before the Deadline
Moving before the 2027 deadline is not optional for organisations that still rely on PSTN or ISDN – it is the only way to keep those services running. When the old copper network is finally switched off, anything still connected to it will simply stop working, creating both operational and financial risk for businesses that have not prepared.
If you reach the deadline without upgrading to digital services, you could see:
Putting off migration often feels easier day‑to‑day, but it usually increases overall cost and risk. Businesses that wait until the last moment typically face:
When PSTN and ISDN are finally switched off, every line still on copper has to move somewhere – usually to an internet‑based phone service. For most UK organisations, the natural replacement is a VoIP or cloud phone system, where calls travel over your broadband instead of fixed telephone lines. Some businesses prefer SIP trunking that plugs into an existing IP‑enabled PBX, but the goal is the same: keep numbers working, support remote staff and stop relying on ageing analogue lines. Looking at these options early gives you time to compare costs, features and reliability, instead of accepting whatever is available in a last‑minute rush before 2027.
VoIP (Voice over Internet Protocol) takes your voice, turns it into digital data and sends it over an internet connection, rather than over copper landlines. Staff can make and receive calls on IP desk phones, softphones on laptops or mobile apps, while you still keep your main business numbers and call routing.
Cost efficiency: Often lower line rental and call charges, plus less on site hardware to buy, power and maintain.
Scalability: New users and numbers can usually be added or removed in a few clicks, which helps with growth or seasonal peaks.
Features: Call queues, routing, voicemail to email, basic analytics, recording and CRM/helpdesk integrations are commonly built in.
Business continuity: Because the service is cloud based and not tied to one building, it is easier to keep phones running during office moves, outages or home working.
As the UK moves fully to all‑IP networks, VoIP lines up directly with where the infrastructure is heading, while PSTN and ISDN are being shut down. A well‑set‑up VoIP or cloud system can give better flexibility, more features and, in many cases, lower total cost than trying to keep old copper‑based services alive.
When you compare VoIP providers, focus on a few essentials instead of long feature lists.
Independent VoIP guides and migration articles from specialists such as VoIP Shop are useful for checking these points and building a short list before you talk to sales teams.
Download the VoIP Shop Migration Brochure (Free PDF)
Get a clear breakdown of features, pricing, migration steps, and network requirements to help you shortlist the right VoIP provider before the 2027 switch off.
The right partner reduces risk during transition, protects mission‑critical lines and ensures long‑term value from new telephony. Strong post‑go‑live support is essential for adoption and resilience.
List every PSTN/ISDN line and connected device, including alarms, lift lines and EPOS.
Compare reliability, SLAs, migration help and contracts.
Check connectivity, bandwidth and QoS readiness for VoIP.
Move low‑risk lines first, then core numbers and emergency lines.
Required bandwidth and QoS
VoIP needs a stable internet line with enough bandwidth for calls, plus normal browsing. If possible, turn on simple QoS, so voice traffic is given priority and calls stay clear when the connection is busy.
Compatible devices
Make a quick list of phones, headsets, conference units, routers and switches, then check which already support IP and which need replacing or an adaptor. This avoids surprises on go‑live day.
Ensuring business continuity
Decide in advance how you will take calls if the main office line or internet fails—backup broadband or 4G/5G, and simple call‑forwarding to mobiles or another site are usually enough for most SMEs.
Migration costs
Plan for some one‑off spend on IP handsets/headsets, any connectivity upgrade, and a bit of setup or project time if your environment is complex.
Long‑term savings
Over time, most businesses save through lower line rental, cheaper calls and no ageing PBX to maintain, while modern features and integrations help staff handle calls more efficiently.
It is the date when the UK’s old PSTN and ISDN landline networks are finally retired and replaced with all‑IP services. That matters because any phones, alarms, lift lines or other systems still on copper lines will no longer work after the switch off.
Start by listing every line and device that still uses a traditional phone connection, then speak to your provider or an independent specialist about VoIP or other digital options. Give yourself enough time to test new services, train staff and move in stages rather than trying to change everything in one week.
VoIP (Voice over Internet Protocol) sends your calls over an internet connection instead of copper phone lines. It is popular because it usually offers more features, easier remote working and lower long‑term costs than maintaining legacy PSTN or ISDN services.
Look at how many people you need to support, how many calls you handle, and how much of your team works remotely, then compare providers on features, reliability and price. Independent guides and comparison tools can help you narrow down a shortlist before you speak to sales teams.
Once the network is switched off, PSTN and ISDN lines will stop working, so you risk losing calls and seeing alarms, lift lines, and payment systems fail. Leaving it late also tends to mean higher engineering costs and less choice, because you are moving under time pressure rather than on your own schedule.
In most cases, yes – your numbers can be “ported” from the old provider to the new VoIP or cloud platform, and this process is protected by Ofcom rules on number portability. Your new provider normally manages the porting for you, but you should plan it carefully so there is no gap in service while the numbers move.
Early movers report smoother projects, no last minute outages and better hybrid work support via cloud telephony. Late movers often face device surprises, limited testing time and VoIP issues on congested or unsuitable networks.
Organisations migrating ahead of the rush typically avoid emergency engineering, maintain inbound service and control costs. Cloud‑based systems also enable flexible working across offices and remote teams.
Leaving migration until the last months, overlooking device dependencies and neglecting network readiness are the most common pitfalls. Each increases the risk of downtime and unplanned spend.
Use a focused checklist to map affected lines/devices, prioritise services and schedule a low‑risk cutover before 2027. Offering the checklist can also support lead generation and position your brand as a practical authority on the BT landline switchover.
To help UK businesses plan for the Big Switch Off 2027, these resources provide detailed guidance, comparisons, and practical advice:
About ComparePhoneSystems:
At ComparePhoneSystems, we provide UK businesses with reliable, up-to-date guidance on the evolving telecom landscape, including critical updates like the big switch off 2027 and the BT landline switchover 2027. Our team brings deep expertise in business communications and phone system solutions, helping organisations understand the implications of the IISDN in the UK. With coverage across the UK and a focus on practical, actionable guidance, we aim to make complex telecom changes simple and understandable for every business.
