The UK’s old analogue phone network is being retired by 31 January 2027, and the deadline affects more than desk phones. Any system that still relies on a traditional PSTN or ISDN line, such as an intruder alarm, lift emergency phone, card terminal, fax or door entry system, needs checking before the switch.
The date has already moved back from the original December 2025 target, but Openreach has said the January 2027 deadline is now locked. If your business still has legacy lines, do not assume your provider will solve every dependency automatically.
This is not only about voice calls. The switch-off retires the Public Switched Telephone Network and the ISDN services that many older office phone systems still use. Some broadband services that depend on a traditional phone line may also need to move to an IP-based alternative. The old network is being replaced because it is harder and more expensive to maintain, which is the same logic behind the push to move off legacy Windows.
Openreach stopped selling PSTN-based copper products nationally in September 2023, and in early 2026 it warned that more than half a million business premises lines still needed to migrate.
Devices that quietly use a phone line
The biggest risk is the kit nobody thinks of as a phone. Plenty of devices have dialled out over a copper line for years, unnoticed. A quiet audit of everything plugged into a phone socket is the most useful thing you can do now. The same “we did not know that depended on it” surprise that caught firms out in the M&S and Co-op disruption applies here, except this deadline is visible.
| System | What it does | What could happen if it is not migrated |
|---|---|---|
| Intruder and fire alarms | Auto-dial a monitoring centre | Monitoring or alerting can fail |
| Lift emergency phones | Call for help from inside a lift | Emergency calling may stop working |
| Door entry and gates | Let visitors call in and release access | Intercom or remote release can fail |
| Card and payment terminals | Process payments through a dial-up line | Transactions may stop processing |
| Fax and franking machines | Send documents or connect to postage systems | The line may no longer work |
| Broadband tied to a phone line | Carries internet over legacy infrastructure | May need moving to fibre or an IP-based service |
What replaces it?
For most offices, the replacement is internet-based calling. That may mean hosted VoIP, Teams calling, SIP trunking for an existing PBX, or another IP telephony service. Calls run over broadband, so reliable connectivity and sensible network foundations matter.
Many businesses are also folding calling into Microsoft 365 and cloud services, so voice, chat and files sit closer together. In that setup, the Teams features you may not be using become more relevant.
You should usually be able to keep existing phone numbers when moving to a digital service, but number porting and provider coordination take time. Start early, especially if you have multiple sites or specialist equipment.
Watch the catches
An old analogue phone could work in a power cut because power came through the line. VoIP does not work that way. If the power or broadband fails, phones may fail too unless you plan for battery backup, mobile failover or another resilience option.
That matters most for lifts, alarms, care systems and emergency lines, where a dead connection is a safety issue rather than an inconvenience. Speak to your alarm, lift, payments and door entry suppliers, not just your telecoms provider.
There is a security side too. Once calls and admin portals move online, weak passwords and stolen credentials can lead to toll fraud and large bills. Apply the same hygiene you use elsewhere, including phishing protection, dark web credential checks and a plan to test the new setup once it is live.
Plan it as a managed project
None of this is dramatic, but it takes planning. Legacy line charges have already been rising to push migration, and a late-2026 rush is likely as more businesses realise what is still connected.
Treat this as a managed migration project, not a January scramble. If you run more than one site, IT support for offices abroad and support across your European sites can keep the rollout consistent. Reading the wider Microsoft 365 pricing and security changes alongside it also helps you budget properly.
Frequently asked questions
When is the PSTN switch-off?
BT’s PSTN is due to be retired by 31 January 2027.
What could stop working?
Analogue and ISDN phone lines, and connected devices such as alarms, lift phones, card machines, door entry systems and fax machines, may stop working if they rely on the old network.
Can I keep my phone number?
Usually, yes. Existing numbers can normally be moved to a VoIP or IP-based service, but the process should be planned in advance.
Will VoIP work in a power cut?
Not without resilience planning. You may need battery backup, mobile failover or another emergency option.
Get the audit done now
The businesses caught out in 2027 will be the ones that only counted their handsets. If you would like a clear audit of every line and connected device, and a calm plan to move them before the deadline, talk to Northern Star’s managed IT team and we will help you switch over without anything going quietly dark.
