By January 2027, the UK’s entire traditional telephone network will be switched off. Not upgraded, not retired gradually — switched off. Every business still running on analogue phone lines, ISDN circuits, or FTTC broadband delivered over copper will either have migrated to a modern alternative or simply have no working phone service.

This isn’t a rumour or a distant plan. BT Openreach confirmed the deadline years ago and has been working through a regional rollout. Some areas of the UK have already had their PSTN switched off as part of the programme. The January 2027 national deadline is real, and it is approaching faster than many businesses realise.

The hard deadline: After January 2027, traditional PSTN and ISDN lines will simply stop working. There is no extension available and no grandfather period. Any business that hasn’t migrated will need to scramble for a new solution at exactly the moment when every other business in the same position is doing the same — driving up wait times and installation lead times significantly.

What is the PSTN and why is it being switched off?

PSTN stands for Public Switched Telephone Network. It’s the copper wire infrastructure that has carried telephone calls across the UK since the late 1800s. Incredibly, a lot of it is still the same physical network — maintained, extended, and patched over more than a century, but fundamentally the same copper.

The problem is that copper is expensive to maintain, cannot support modern broadband speeds, and is simply not fit for the way businesses now communicate. BT has been investing heavily in full-fibre infrastructure — fibre optic cables that run all the way to the premises — and the PSTN is being retired to fund and focus that investment. The switch-off was delayed once (the original deadline was December 2025) but January 2027 is firm.

What exactly is affected?

More than many businesses realise. The obvious things are phone lines and ISDN systems. But there are less obvious services that also run over PSTN that can catch businesses out:

  • Traditional landline phone systems — any system connected to an analogue or ISDN line
  • ADSL and FTTC broadband — if your broadband arrives over a copper phone line, that line will be switched off
  • Alarm diallers — many intruder alarms and fire alarms dial out over PSTN when triggered
  • Lift emergency phones — legally required in many buildings, often connected to PSTN
  • Door entry and access control systems — some use analogue lines for external communication
  • EPOS and payment terminals — older card machines that dial up rather than using IP
  • Fax machines — still in use in some professional services and healthcare settings
⚠️ Easy to miss

The alarm dialler issue catches a lot of businesses off guard. Your intruder alarm or fire alarm may have a PSTN connection that you’ve never needed to think about before. After January 2027, if it hasn’t been migrated to a 4G or IP alternative, it won’t be able to contact the alarm receiving centre if it triggers. A site survey is the safest way to identify every PSTN-connected device on your premises.

What’s the replacement?

For phone systems, the answer is VoIP — Voice over Internet Protocol. Rather than calls travelling over a dedicated copper line, they travel over your broadband connection using the same internet infrastructure you use for everything else. Modern VoIP systems are indistinguishable from traditional phone systems in call quality, and they add a significant range of features that copper lines simply cannot provide.

For most Yorkshire businesses, the migration involves two things: replacing the phone system itself with a hosted VoIP platform, and — if your broadband was delivered over copper — moving to a full-fibre or alternative broadband connection. In many cases, businesses that do this end up with lower monthly costs than they were paying for their old ISDN lines.

💡 The upside of migrating

VoIP isn’t just a like-for-like replacement. You get features that were enterprise-only under the old system: mobile apps so staff can take business calls on their phones, call recording, voicemail delivered to email, call queues and auto-attendants, and the ability to add or remove extensions in minutes rather than waiting for an engineer. Most businesses see their monthly phone costs fall by 30–50% after migrating from ISDN to hosted VoIP.

How long does migration take?

A straightforward migration — a single-site business, existing broadband infrastructure, standard requirements — typically takes two to four weeks from order confirmation to go-live. That includes number porting (keeping your existing phone numbers), hardware delivery, configuration, and testing. More complex setups with multiple sites, large call volumes, or integrations with other systems take longer.

The businesses that are going to struggle are the ones that leave this until October or November 2026. By then, every IT and telecoms provider in the country will be dealing with a last-minute rush. Installation lead times will be longer, there will be less flexibility to schedule around your business needs, and there’s a genuine risk of running up against the January deadline.

BOOM I.T. supplies and manages VoIP phone systems for Yorkshire businesses. If you’re not sure whether you’re affected, or you want to start planning your migration, call us on 03333 660 005. We’ll tell you exactly where you stand and what needs to happen — and there’s no obligation to proceed with us.