The short answer: BT is retiring the old copper telephone network (PSTN and ISDN) and replacing it with a digital Voice over IP (VoIP) system. The switch-off is planned to complete by January 2027. For most people, this means their home phone will need to work via their broadband router rather than directly through a phone socket. Broadband itself is largely unaffected, but equipment connected to the old phone line may need updating.
What is the PSTN and why is it being switched off?
The Public Switched Telephone Network (PSTN) is the traditional copper wire telephone infrastructure that has formed the backbone of UK phone communications for decades. Most homes with a landline have a physical copper cable running from a BT exchange to a socket on the wall. ADSL and FTTC broadband also use this copper infrastructure.
BT Openreach announced in 2019 that it would retire the PSTN and ISDN networks entirely, replacing them with digital Voice over IP (VoIP) services. The deadline for completion is January 2027, though the switchover is being completed area by area, with some exchanges already completed.
The reason for the switch-off is straightforward: the copper network is ageing, expensive to maintain, and incompatible with the full fibre (FTTP) rollout. Full fibre connections carry only data; voice calls must run as data over the internet rather than through a dedicated circuit.
What changes for your broadband
If you are already on full fibre (FTTP), the switch-off has essentially no impact on your broadband connection. FTTP already works independently of the copper phone line.
If you are on FTTC (superfast fibre) or ADSL, your broadband currently runs partly or entirely over the copper network. When the PSTN is retired in your area, your provider will need to migrate your connection to either full fibre or a digital alternative. In most cases, this will mean being upgraded to full fibre if it is available, or remaining on an alternative fixed technology.
Your broadband provider will contact you before the switch-off affects your area. You should not need to do anything proactively unless you have specific equipment connected to the phone line. If your provider has not contacted you and you want to know when your exchange is scheduled for switchover, contact them directly.
What changes for your home phone
This is where most households will notice a change. After the switch-off, you will no longer be able to plug a standard telephone into the BT socket on the wall and get a dial tone. Voice calls will need to travel over your broadband connection using VoIP technology.
In practice, most providers will supply a new router with built-in phone ports, or an adapter that connects your existing phone to the router. Your phone number stays the same. The handset you use can remain the same. The change is primarily in how the call is routed, not how you make it.
Cordless (DECT) phones
Standard cordless DECT phones will continue to work after the switch-off, provided they are connected to the router or an approved adapter rather than directly to the phone socket. Most modern routers supplied by UK broadband providers have a phone port built in for exactly this purpose.
Older analogue phones
Older analogue phones can continue to be used via an analogue telephone adapter (ATA), which converts the analogue phone signal into a VoIP signal. Your provider may supply one, or you can purchase one independently.
Equipment that may be affected
Beyond the home phone itself, other equipment connected to the phone line may stop working correctly after the switch-off. This is worth checking for each item in your home.
Burglar alarms
Many older alarm systems use the phone line to alert monitoring centres when triggered. If your alarm uses a telephone dialler to communicate, it will stop working when the PSTN is retired. Contact your alarm provider or monitoring company to check whether your system is compatible with VoIP and whether an upgrade is needed. This is one of the more important things to check before the switch-off reaches your area.
Telecare and personal alarm systems
Personal alarms used by elderly or vulnerable people often rely on the telephone line to contact a care centre when the button is pressed. These systems need to be updated before the switch-off. The government and NHS have committed to ensuring vulnerable users are protected, and providers are required to proactively contact customers with known telecare equipment. If you or someone you care for uses a telecare device, contact both the care provider and the broadband provider to confirm the device will work on a digital line.
Fax machines
Fax machines that use the phone line will not work on a VoIP service without specific compatibility settings. Most VoIP systems can cause issues for fax transmission because of the way they handle data. If you or your business relies on a fax line, check with your provider about dedicated fax solutions or alternatives.
Payment terminals
Older card payment terminals that dial out over a phone line are also affected. Most modern payment terminals already use mobile data or broadband rather than the PSTN, but older installations in small businesses may need upgrading.
Home lifts
Some residential lifts have emergency phones that use the telephone line. Check with the lift maintenance company whether yours is compatible with digital services.
Power cuts and the VoIP phone
This is an important practical difference between the old copper network and the new digital system. The PSTN carried its own power, meaning your phone continued to work even when the mains electricity was off. A VoIP phone depends on your router, which depends on your mains power supply. If the power goes out, your home phone will also be out.
Ofcom has required that all providers give customers who rely on their landline a means of making calls during a power cut. In practice this usually means ensuring you have a mobile phone that can be used as a backup. Providers are required to proactively identify customers without an alternative means of communication and offer them a suitable solution, such as a battery backup unit or a SIM card for emergency use.
If you or someone you support has no mobile phone and relies entirely on their landline, contact your broadband provider now to discuss options. Ofcom requires providers to support these customers with a backup solution before the switch-off affects their area.
When is the switch-off happening?
BT Openreach committed to completing the full switch-off by January 2027. The process is being done in stages, exchange by exchange. Some areas have already completed the transition. Others are still on the original PSTN. Your provider will contact you in advance when your area is approaching the switchover date.
The original completion date was December 2025, but BT pushed this back to January 2027 following concerns about the readiness of some consumer groups, particularly elderly and vulnerable customers who may need additional support during the transition.
What you need to do
For most households with a standard broadband and phone package, the answer is relatively little. Your provider will contact you, update your service, and either supply new equipment or tell you what changes are needed to your existing setup. The transition is designed to be as seamless as possible for residential customers.
The practical steps worth taking now:
- Check whether any equipment in your home (alarm, telecare device, fax) uses the telephone line. Contact the relevant suppliers to confirm compatibility.
- Make sure you have a working mobile phone or another way to make calls if there is a power cut.
- If you or someone you care for relies entirely on a landline and has no mobile phone, contact your broadband provider to discuss backup options.
What you do not need
- You do not need to upgrade your broadband ahead of the switch-off yourself. Your provider will manage the migration and contact you in advance. You do not need to proactively switch to full fibre because of the PSTN retirement, though doing so is a good idea for speed and reliability reasons.
- You do not need a new phone handset. Existing handsets continue to work via a phone port on the new router or an analogue telephone adapter. Your number stays the same.
- You do not need to panic about your broadband stopping. The switch-off primarily affects voice services. Broadband connections are migrated as part of the transition and providers are responsible for ensuring continuity of service.
- You do not need to accept a degraded service. If your connection quality changes during the transition and your provider cannot resolve it, you have standard consumer rights, including the right to escalate the complaint and exit your contract if the issue is not fixed within 30 days.
Frequently asked questions
Will my broadband stop working when the PSTN is switched off?
No. Your broadband provider will manage the transition for you. For customers on FTTC or ADSL who need to be migrated, the provider will arrange this and contact you beforehand. For customers already on full fibre, there is essentially no change to broadband. The switch-off primarily affects voice calls made through the traditional phone socket.
Will my phone number change?
No. Your existing landline number carries over to the new VoIP service. You keep the same number and the same handset. Calls come and go in exactly the same way from your perspective. The only difference is that the call travels as data over your broadband connection rather than as an analogue signal over copper.
My alarm system uses the phone line. What do I do?
Contact your alarm installer or monitoring company as soon as possible. Ask whether your system is compatible with VoIP or whether it needs an upgrade. Many monitoring companies have already begun proactively contacting customers, but do not wait to be contacted if you have a functioning alarm that uses a telephone dialler. The deadline for the switch-off is January 2027, which sounds distant but installations and upgrades take time to arrange.
Does the PSTN switch-off affect mobile phones?
No. Mobile phones use separate mobile network infrastructure and are entirely unaffected by the PSTN retirement. The switch-off only affects fixed landline connections.
What if I only have a landline and no mobile phone?
Ofcom has rules requiring providers to ensure that vulnerable customers, particularly those with no alternative means of communication, are given a backup solution before the switch-off reaches their area. Contact your broadband and phone provider now to make them aware of your situation. They are required to offer you a suitable option, such as a battery backup for your VoIP phone or a basic SIM card for emergency use.
I am still on ADSL broadband. Will the switch-off force me to upgrade?
ADSL runs over the copper PSTN, so yes, the switch-off will require your connection to be migrated. Your provider will handle this and contact you in advance. In most cases, they will offer you an upgrade to full fibre if it is available at your address, or a digital alternative. You will not be left without a service, and you should not face additional charges for the migration itself. If your provider tries to charge you for a forced upgrade resulting from the PSTN retirement, challenge it.