Across the UK, businesses still relying on legacy telephony are facing rising costs, inefficiencies, and a looming deadline: the national PSTN and ISDN switch-off. With BT planning to shut down the traditional copper-based network by the end of 2025, time is running out for organisations to modernise their communications infrastructure.
Failing to act now means more than just higher bills and frustrated employees—it could mean losing your phone service entirely.
Failing to act now means more than just higher bills and frustrated employees—it could mean losing your phone service entirely.
The 2025 Deadline Is Closer Than You Think
BT has confirmed that the Public Switched Telephone Network (PSTN) and Integrated Services Digital Network (ISDN) will be fully switched off by January 2027. This includes all traditional landlines and any services that rely on them—including phones, fax machines, alarms, payment terminals, and lift lines.
For businesses still using these services, that’s less than 18 months to find and implement a future-proof alternative.
For businesses still using these services, that’s less than 18 months to find and implement a future-proof alternative.
What Does This Mean for Your Business?
If you haven’t made the switch, you’re at risk of:
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Losing all landline connectivity
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Increased disruption and downtime
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Rushed decisions and last-minute migrations
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Higher costs as suppliers prioritise urgent upgrades
The closer we get to the deadline, the more demand will spike for engineers, hardware, and cloud migration services—which could delay your transition and increase costs.
Step 1: Audit Your Current Setup
Start by identifying exactly what parts of your infrastructure still rely on PSTN or ISDN. This might include:
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Traditional desk phones
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On-premise PBX systems
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Door entry systems
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Alarm lines
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Card machines
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Lift emergency lines
You might be surprised how many systems are still connected to legacy lines.
Step 2: Plan Your Migration Strategically
Moving away from legacy telephony doesn’t mean starting from scratch. The smartest route is often a phased migration—especially if you choose a flexible solution that integrates with your existing tools and infrastructure.
Many businesses are choosing to migrate to cloud-based phone systems that run over the internet, often integrated with platforms like Microsoft Teams for a unified communication experience.
Many businesses are choosing to migrate to cloud-based phone systems that run over the internet, often integrated with platforms like Microsoft Teams for a unified communication experience.
Step 3: Look Beyond Telephony Alone
This isn’t just an opportunity to replace one phone system with another—it’s your chance to:
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Consolidate your communications stack
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Integrate voice, video, chat, and CRM
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Streamline operations and reduce cost
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Enable remote and hybrid working
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Future-proof your setup with AI and automation
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Lift emergency lines
In other words, the switch-off isn’t just a deadline—it’s an opportunity to modernise how your business communicates.
Step 4: Don’t Leave It Too Late
Leaving your migration until the last minute could lead to rushed decisions, downtime, and unexpected costs. The earlier you start, the more time you have to choose the right solution, roll it out smoothly, and train your team.
Need Help Navigating the Switch-Off?
We’ve put together a practical guide to help you understand what the switch-off means, what systems are affected, and how to plan your move.
Read everything you need to know about the 2027 Switch-Off in our PSTN blog section.
Read everything you need to know about the 2027 Switch-Off in our PSTN blog section.
