What is being switched off and why
The PSTN is the traditional copper-wire network for landline voice calls, in service in the UK for many decades. Communications Plus+1
ISDN is the digital upgrade to PSTN lines (e.g., ISDN2, ISDN30) used chiefly by businesses. Spitfire Network Services Ltd+1
These networks are being withdrawn because maintaining ageing copper infrastructure is increasingly costly, less reliable and ill-suited to modern digital communication needs. cambridgemc.com+1
The replacement is a fully digital, Internet-based voice network (VoIP), often delivered over fibre broadband. Vodafone+1
Key dates and timeline
In many regions, the “stop-sell” of new analogue lines began in September 2023: new orders for PSTN/ISDN services are no longer available. Spitfire Network Services Ltd+1
The final decommissioning deadline is 31 January 2027 for all PSTN/ISDN services. Claranet+1
Providers encourage migration sooner rather than later — the extension is not a reason to delay. Spitfire Network Services Ltd+1
Who will be affected
Residential users
Anyone with a traditional landline phone service over PSTN will need to switch to a digital alternative (VoIP/home digital phone line). Openreach+1
Devices that relied on the copper line (e.g., home alarms, health pendants, lift emergency lines, older fax machines) may be impacted and require checking for compatibility. cambridgemc.com+1
Businesses and public sector
Many businesses still rely on ISDN lines, analogue voice trunks, or services tied to copper infrastructure. These will need migrating. Computer Weekly+1
Critical services (healthcare alarms, telecare, payment terminals, building management systems) must ensure continuity of service when the legacy network goes. cambridgemc.com
Benefits and risks
Benefits
Modern digital voice services offer more flexibility (mobile integration, cloud PBX, SIP trunks) and often lower cost. The VoIP Shop+1
Upgrading gives an opportunity to modernise comms infrastructure and future-proof for several years ahead. BT Business
Risks if you delay
If you are still on PSTN/ISDN when the network is switched off, you risk losing voice services, incurring major disruption. texaport.co.uk+1
Some older equipment may cease to function (analogue alarms, faxes) unless adapted for digital services. Openreach+1
As the deadline looms, migration resources (engineers, fibre rollout) may become constrained, potentially increasing cost or delay. Spitfire Network Services Ltd
What you should do now
Here’s a checklist to guide your preparation:
Audit your current setup: Identify all connections using PSTN/ISDN—landlines, fax, alarms, lift-lines, payment terminals. fidelisplus.com
Check broadband readiness: Ensure you have reliable internet of sufficient bandwidth, as the digital voice service will rely on it. Openreach+1
Discuss migration with your provider: Find out which digital voice service (VoIP/SIP) and broadband option is best suited, costs, whether you can keep your existing number etc. Openreach+1
Upgrade any legacy systems: For devices tied to copper lines, ensure digital alternatives or adaptors are in place. E.g., telecare alarms, PDQ terminals. texaport.co.uk
Plan early and test: Migrate ahead of the deadline, test your new setup to ensure calls, emergency numbers and any dependent services work. Don’t wait till the last minute. Spitfire Network Services Ltd
Implications for businesses (UK)
If your business still uses ISDN or analogue trunks, switching to digital now can improve flexibility (remote workers, integrations) and reduce reliance on outdated hardware. Gamma Communications+1
As you migrate, consider whether you need full fibre (FTTP) or single order broadband (SOGEA) as part of the transition. Vodafone
Make sure any business-critical systems (alarm monitoring, PDQ machines, fire/lift systems) are compatible with the new voice/broadband architecture. Claranet
Review your contracts and exit/termination terms for legacy services: as legacy lines get withdrawn, costs may increase or support may be withdrawn. Claranet
Final thoughts
The January 2027 deadline for the UK PSTN/ISDN switch-off is a major milestone in the country’s shift to a modern communications infrastructure. While the transition may seem daunting, it presents a genuine opportunity to upgrade and streamline your voice and broadband services. The key is to act now: delaying increases risk, whereas early migration allows smoother transition and positions you for future-proof communications.