The UK’s nationwide switch-off of the traditional telephone network has a confirmed final deadline: 31 January 2027. The original 2025 target was pushed back industry-wide to allow for a smoother transition, particularly for vulnerable consumers and critical care users, but the deadline is now firm.
If your business still relies on traditional landlines, ISDN lines, or any equipment connected through the old network, it’s worth understanding what’s changing and what to do about it well before the deadline arrives.
What’s actually being switched off
The Public Switched Telephone Network (PSTN) and Integrated Services Digital Network (ISDN), the traditional infrastructure behind landline telephones, analogue lines, and old-style business phone systems, are being retired nationwide. They’re being replaced entirely by internet-based (all-IP) communication technology.
This isn’t just about phone calls. Anything still connected through an old analogue or ISDN line, alarm systems, payment terminals, fax machines, lift lines, and some older security systems, will also be affected and needs to move to an alternative before the switch-off.
Why this is happening
Maintaining the old PSTN infrastructure is expensive and increasingly impractical as the underlying technology ages. Moving to all-IP networks lets providers retire that infrastructure and gives businesses access to more flexible, feature-rich communication tools, things that simply weren’t possible on the old network.
What this means for your business
If you’re already using Microsoft Teams calling, you have nothing to worry about, your phone system already runs over the internet rather than the old network. See our Microsoft Teams Calling page for what this looks like in practice.
If your business still relies on a traditional phone line or an older on-premise phone system, you need a plan before January 2027. The good news is that the alternative is usually a genuine upgrade, not just a forced change.
What we recommend
For most London SMEs already using Microsoft 365, Microsoft Teams calling is the natural replacement: one phone number, working across desktop, mobile, and desk handsets, managed from the same platform as your email and collaboration tools, with no separate phone provider or hardware contract to manage. See our Microsoft Teams Calling page for full detail.
If your business currently runs 3CX, we continue to support and maintain existing 3CX deployments for clients who are happy with their current setup. 3CX itself already runs over IP rather than the old PSTN network, so existing 3CX clients are not directly affected by the switch-off, though it’s worth discussing whether moving to Teams calling would now make more sense for your business. See our 3CX support page.
What to check before the deadline
A few things worth reviewing now rather than close to the deadline:
- Any alarm systems, payment terminals, or fax lines still connected via an analogue or ISDN line will need an alternative arranged with the relevant provider directly.
- If you’re not certain which parts of your business still rely on the old network, this is worth checking as part of a wider review, particularly for older equipment that’s been in place for years without anyone thinking about how it actually connects.
- Speak to your telecoms or broadband provider directly about their specific switch-off timeline for your line, as providers are migrating customers on a rolling basis ahead of the final deadline.
One monthly fee. One number to call. If your business needs to plan its move away from the old telephone network, we can help you get set up on Microsoft Teams calling well ahead of the deadline.
