Most businesses are aware that the UK’s PSTN and ISDN networks will be switched off on 31 January 2027.
What we’re finding though is that many organisations are still working towards that date, when the real pressure point is much earlier.
If you’re still using PSTN or ISDN services, migration orders should be submitted before 30 September 2026 if you want the best chance of completing your move before the switch-off.
At first glance that might not sound like a problem. After all, January 2027 still feels some way off.
The issue is that replacing a phone line is rarely the hard part.
At a Glance
- The UK’s PSTN and ISDN networks will be switched off on 31 January 2027
- Organisations still relying on legacy services should be planning their migration now
- 30 September 2026 is the key date for submitting migration orders
- The biggest risk is often not the phone system itself, but the services connected to it
- Many businesses still have alarms, lift phones, payment terminals and access control systems relying on legacy connectivity
- Leaving migration too late increases the risk of disruption and rushed decision-making
- The switch-over is also an opportunity to review communications, connectivity and resilience across your wider estate.
The issue is that replacing a phone line is rarely the hard part.
What catches organisations out is everything that has been connected to those lines over the years.
We’ve spoken to businesses that knew about their phone system but hadn’t considered alarm signalling, lift emergency phones, access control systems, card payment machines or building management systems. In many cases, these services have been in place for years and nobody has questioned how they’re connected.
That’s where the risk sits.
The Services People Often Forget About
Phone systems are usually the obvious one. The hidden risks are often:
- Alarm systems
- Lift emergency phones
- Door entry systems
- Payment terminals
- Building management systems
- Security and monitoring solutions
Many organisations have technology that was installed years ago and has quietly remained connected ever since.
The problem is often not the phone line itself. It’s the critical service attached to it.
Why Waiting Creates Risk
The closer we get to January 2027, the less time there is to uncover those dependencies, decide what needs replacing and put a plan in place.
For some organisations, that could be a fairly straightforward exercise. For others, particularly those operating across multiple locations, it can become a much larger project once you start identifying what’s actually relying on legacy connectivity.
The businesses most at risk aren’t necessarily those with the oldest technology. They’re the ones that don’t have visibility of what’s connected across their estate.
This Is More Than A Telephony Project
We don’t see the digital switch-over as purely a telephony project.
It’s about understanding what could stop working, what impact that would have on the business and how you avoid disruption when the switch-off finally arrives.
Many organisations are using the transition as an opportunity to review:
- Legacy communications platforms
- Connectivity resilience
- Hybrid working requirements
- Security and compliance considerations
- Wider infrastructure strategy
The businesses that are making good progress aren’t necessarily the ones with the newest infrastructure. They’re the ones that have started asking the right questions early enough.
Are you ready?
A Quick Readiness Check
Ask yourself:
✓ Do we know where PSTN or ISDN services still exist?
✓ Have we identified what’s connected to them?
✓ Do we understand the impact if those services disappear?
✓ Do we have a clear migration plan?
✓ Have we already started the process?
If you’re unsure about any of those answers, now is the time to take a closer look.
