What is being switched off
The Public Switched Telephone Network (PSTN) is the analogue copper network that has carried landline calls for decades. ISDN, the digital service many businesses used for multiple lines, runs over the same infrastructure. Openreach has been withdrawing these services and moving the UK to fibre and internet-based voice.
Openreach has said 31 January 2027 is the fixed date for retiring the PSTN, and that lines still on the old network will be phased out progressively. Unmigrated lines have also faced substantial wholesale rental increases through 2026, so staying put is getting more expensive as well as riskier.
What it affects
Phone lines are the obvious part. The bigger risk is equipment that quietly uses a phone line and that nobody has looked at for years.
- Analogue phones, fax machines and old PBX systems
- ISDN2 and ISDN30 lines
- Intruder and fire alarm diallers
- Lift emergency phones and door entry systems
- Older card payment terminals that dial out
- Franking machines, CCTV dial-ups and telemetry
- Telecare and health alarms
What replaces it
Voice moves to internet-based services. For most businesses that means a cloud VoIP phone system or Microsoft Teams calling. If you have a recent on-site PBX, SIP trunks can connect it to the internet instead. Single lines can move to a digital line product that plugs into a router.
Connectivity changes too. Broadband without a phone line (SoGEA) and full fibre (FTTP) replace broadband-plus-landline packages. Devices such as alarms may need a 4G communicator or an IP-based dialler.
A five-step plan
- List every line: get recent bills and match each number to a location.
- Find out what is plugged into each line, especially in plant rooms and lift shafts.
- Ask alarm, lift and payment providers to confirm compatibility in writing.
- Choose replacements for voice, data and each device.
- Schedule migrations line by line and test each device after it moves.
Do not assume your provider will contact you in time. Openreach has warned businesses not to wait.
Will I lose my numbers?
No. Numbers can be ported to VoIP, SIP or digital line services. Plan the port as part of your migration so the number moves when the service does.