Updated July 2026: UK businesses using traditional telephone lines now have a firm deadline to plan around. Openreach customers must be migrated away from the legacy Public Switched Telephone Network (PSTN) and ISDN services by 31 January 2027. This is not simply a telephone-system change: many alarms, lift phones, door-entry systems, fax machines, payment terminals and other devices can still depend on an analogue line.
This guide explains what the digital switchover means, what to audit and how to move to modern voice services without creating unnecessary risk for your business.
What is being switched off?
The PSTN is the ageing analogue telephone network that has carried traditional voice services for decades. ISDN added digital voice channels over the same legacy infrastructure and became widely used for business phone systems. These services are being replaced by internet-based, All-IP alternatives.
The current government connectivity timeline states that all users of the Openreach PSTN need to be migrated by 31 January 2027. Individual providers may move customers earlier, so businesses should confirm their own migration timetable rather than waiting for the final deadline.
Read the current UK government telecommunications timeline.
The hidden services your audit must include
Start with every telephone number and line on your bills, but do not stop there. Legacy connections are often hidden inside facilities, security and operational systems.
- Business telephone systems and individual analogue handsets
- Lift emergency phones and refuge communication systems
- Fire, intruder and monitored alarm signalling
- Door-entry systems, intercoms, gates and barriers
- Fax machines, franking machines and analogue modems
- EPOS, card-payment and vending equipment
- Telemetry, building-management and remote-monitoring devices
- Redcare-style signalling and other supplier-managed services
Record the number, location, supplier, purpose, contract owner and business impact of losing each service. Ask the equipment manufacturer whether the device is approved for use over an IP connection—an analogue telephone adaptor is not suitable for every system.
Replacement options for business voice
Hosted VoIP
A hosted telephone system moves the call-control platform into the cloud. Users can work with desk phones, desktop software and mobile applications, while features such as call groups, voicemail-to-email, reporting and business-continuity routing are managed centrally. It is often the simplest option for organisations replacing an older PBX.
SIP trunks
SIP trunks carry calls over an IP connection and can allow a compatible on-premises phone system to remain in service. Compatibility, software support, licensing and resilience should all be checked before choosing this route.
Digital voice and specialist replacements
A provider-supplied digital voice service may suit a small number of ordinary handsets. Safety-critical or machine-to-machine equipment may need a purpose-built IP or mobile replacement supplied and tested by the relevant alarm, lift or equipment specialist.
Plan for power cuts and broadband failure
Traditional analogue lines could power a basic handset from the exchange. IP phones, routers, switches and fibre equipment require local electricity. A digital migration therefore needs a resilience plan, not only a new telephone contract.
- Use an appropriately sized UPS for routers, switches, telephone equipment and fibre termination devices.
- Consider a second internet connection or managed 4G/5G failover for important sites.
- Configure call diversion or mobile applications for an office outage.
- Test emergency calls, alarm signalling and failover under realistic conditions.
- Document who receives alerts and who is authorised to contact each supplier.
A practical seven-step migration plan
- Audit every line and dependent device. Match bills to equipment and locations.
- Confirm supplier deadlines. Your provider may migrate services before January 2027.
- Separate voice from specialist systems. Involve alarm, lift, payment and facilities suppliers early.
- Assess connectivity. Check bandwidth, latency, Wi-Fi, switching, firewall rules and resilience.
- Select and configure the replacement. Plan number porting, call flows, licences, handsets and user applications.
- Test before ceasing anything. Prove inbound and outbound calls, emergency calling, failover and every connected device.
- Train users and document support. Provide quick guides and clear escalation contacts.
How MSP247 can help
MSP247 can audit your current lines, review network readiness, design a resilient replacement and coordinate number porting and user deployment. Our business telephone systems, connectivity and managed IT services can be brought together through one support team.
Do not wait for a cease notice to reveal a forgotten line. Contact MSP247 to arrange a practical PSTN and ISDN migration review.