In this article
For decades, a UK business phone line has meant a copper wire into the building. That ends soon. BT says the PSTN switch-off happens on 31 January 2027, and after that date any service still on the old network will be lost. If your business still has a traditional landline, this is the moment to move it, and to check everything else plugged into the phone socket.
What is actually switching off
PSTN stands for Public Switched Telephone Network: the old copper network that has carried landline calls since long before the internet. ISDN, the digital line many offices used for multi-line phone systems, is going too. Both are being replaced by phone services that run over broadband, often called All IP, digital voice or VoIP.
BT's guidance is blunt: "To stay connected you'll need to switch to an All IP digital service," and "any remaining services not switched to the new digital network will be lost."
How many businesses are still to move?
A good number. Industry reporting of an Openreach update in July 2026 put the figure at around 1.5 million lines still on the old network, including roughly 350,000 business premises. That figure comes from a secondary source rather than an Openreach document we could check, but the direction is clear: plenty of businesses have not yet moved, and providers will get busier as the date approaches.
It is not just the phone
The phone on the desk is the easy part. The risk sits in the equipment people forget is connected to the line. Openreach lists devices that may be affected:
| Device | Why it matters | Who to ask |
|---|---|---|
| Intruder and fire alarms | Many alarms dial out over the phone line to a monitoring centre. | Your alarm company |
| Card payment terminals | Older terminals may connect over the phone line rather than broadband or mobile. | Your payment provider |
| Lift emergency phones | A legal and safety requirement in many buildings. | Your lift maintenance company |
| Door entry and CCTV | Some systems call out or report over the line. | The installer |
| Telecare and health monitoring | Critical for care settings and vulnerable people. | The care or device provider |
A simple plan for the next few weeks
- 01Call your providerAsk when and how your lines will move, and confirm your numbers will be ported.
- 02List connected devicesWalk the building: anything that plugs into a phone socket goes on the list.
- 03Check each supplierAsk alarm, payment and lift suppliers what changes, and when.
- 04Plan for power cutsDigital phones need power and broadband. Decide what happens if either fails.
The opportunity hiding in the switch-off
Most businesses will treat the switch-off as a box to tick: same phone, same number, new line. But you are changing phone systems either way, and modern digital phone services make it straightforward to add something old landlines could not: a way to answer every call.
For service businesses, a missed call is usually a missed enquiry. The caller rings the next company on the list. Our free missed call cost calculator shows what that adds up to for your business. An AI voice agent can answer when the team is busy or out of hours, take the details, book an appointment or send an urgent call to the right person. Because your new phone service runs over the internet, connecting an AI receptionist to it is a configuration job rather than a building project.
If you are weighing it up, our guides cover what AI voice agents do for service businesses, what they cost in the UK and how they work under the hood. Our AI voice agents service page shows how we build them around your existing calendar and CRM.
The bottom line
The date is fixed and the work is not difficult, but it is easy to leave too late. Call your provider this month, check every device on the line, and decide whether the new phone system should simply replace the old one, or make sure your business never misses a call again.
If you would like to talk through the second option, get in touch and tell us how your calls are handled today.
Frequently asked questions
- When is the PSTN switch-off in the UK?
- BT and Openreach both give 31 January 2027 as the date when traditional copper phone lines go digital. Any service still running on the old network after that date will stop working, so businesses should move to a digital (All IP) service before then.
- Will my business phone number change?
- Normally no. When you move to a digital phone service, your provider can usually port your existing number across. Confirm this with your provider before you switch.
- What else stops working when the copper network switches off?
- Openreach lists alarms, CCTV, payment terminals, telecare devices, health monitoring equipment, door entry systems and lift phones as devices that may be affected. Anything that plugs into a phone socket should be checked with its supplier.
- What should I do first?
- Openreach's advice is to call your service provider as soon as possible. Then list every device that uses your phone line, from alarms to card machines, and ask each supplier how it will work after the switch.
Sources and further reading
Facts, prices and dates in this article were checked against these pages on the dates shown. Vendor prices and regulations change, so check the source before you rely on a figure.
- The UK's PSTN network will switch off in 2027 · BT Business · accessed 6 November 2026
- The Big Switch Off · Openreach · accessed 6 November 2026
- PSTN switch-off 31 January 2027: timeline, status and how to prepare · Connection Technologies · accessed 6 November 2026