The 2027 PSTN switch-off: what UK businesses must sort

Somewhere in your building there's probably a cable you never think about. It feeds the alarm, or the lift phone, or the card machine, or the fax that one supplier still insists on. It has worked for years without a single thought from you. That's exactly the problem.

The PSTN switch-off in 2027 ends the old analogue phone network across the UK, and a lot of kit that quietly rides on those lines stops working with it. Most owners I talk to have heard the phrase and assumed it's a BT problem, not theirs. It's theirs. The good news is the fix is calmer than the headlines suggest, as long as you start before the deadline rather than on it.

Let's do the bit that matters first: what you actually have to check. The history can wait.

What the PSTN switch-off actually means

The "PSTN" is the Public Switched Telephone Network. It's the copper-and-exchange system that has carried UK phone calls for over a century. ISDN, the business version that bundled several lines together, sits on the same retiring infrastructure.

Openreach is retiring all of it and moving voice onto the internet instead. Your calls will travel as data over broadband, the same way everything else you do already does. BT brands its consumer version "Digital Voice"; the general term is calling over the internet, or VoIP.

This isn't a product you can opt out of. It's the network underneath the product going away. Every UK line lands on the new way of working eventually. The only choice you have is whether you move on your terms or have it done to you near the deadline.

The date that actually matters

You can't buy a new analogue or ISDN line anymore. The national stop-sell came in back in 2023, so anything you're running today is already living on borrowed time.

The full switch-off was originally set for December 2025. It got moved. The industry pushed the date to the end of January 2027, mainly to protect vulnerable people who rely on telecare alarms and to give everyone more room to migrate safely. So the working deadline is the end of January 2027, not 2025, and not "whenever BT gets round to it".

That sounds far off. It isn't, once you account for ordering kit, swapping over devices and testing that the important stuff still works. A year goes quickly when the change touches your alarm, your lift and your payments.

What stops working when the line goes dark

Phones are the obvious thing. They're rarely the risky thing. The risk sits in the devices that dial out over an analogue line without anyone realising, and keep doing it until the day they can't.

Check anything in this list that you might have:

• Intruder and burglar alarms that report to a monitoring centre down the phone line
• Lift emergency phones and the autodiallers behind them
• Monitored fire alarms
• Door entry and gate intercom systems
• Card payment machines that dial out instead of using your network
• Telecare and personal pendant alarms, if you run any kind of care setting
• Fax machines, franking machines and older EPOS tills
• CCTV that uploads or alerts over a phone line

There's one more thing worth saying plainly. The old copper line carried its own power, so a basic phone kept working in a power cut. The new way needs broadband and mains power, which means a power cut takes your line with it unless you've planned for backup. For a lift phone or an alarm, that's not a detail. That's the whole point of the device.

What a UK business actually has to do

You don't need a project plan. You need a walk round the building and a few honest questions. Here's the short version.

1. Find every analogue line. Look at your bills and your sockets. Note what's plugged into each one, including the things nobody owns.
2. List the devices that depend on those lines. Alarms, lifts, card machines, fax, anything from the list above. For each, ask: who supports this, and do they have an internet-based replacement?
3. Sort the safety-critical kit first. Lift phones, fire and intruder alarms and telecare can't have a gap. Talk to the people who maintain them now, because they'll have a switch-off plan and a part to play.
4. Decide how your actual phone calls should work. This is the moment to stop patching an old setup and choose something that fits how your team works today, not in 2009 - including whether you need a desk phone at all.
5. Sort out backup power for anything that has to survive a power cut.
6. Move before the rush. Nobody wants to be migrating an alarm in January 2027 alongside everyone else who left it late.

Most of this is a morning's work to map and a few calls to arrange. The mistake isn't getting it wrong. It's not looking until the line's already gone.

Go deeper on the move

This piece is the overview. Two parts are already written up in more detail:

• Keeping your number when you switch - how UK number porting works, and why it isn't a reason to delay.
• Switching provider without downtime - the cutover sequence that keeps disruption to a minimum.

The calm way to handle the phone side

Here's where I'll be straight with you, because we've watched this from the inside. We UC has spent 15 years running UK telecoms, and we've moved a lot of businesses off old lines onto calls over the internet. It's routine when it's planned. It's painful when it's panicked.

The phone part of the switch-off is genuinely an opportunity, not just a chore. Once your calls run over the internet, your number stops being tied to a socket in one building. You keep your existing number, your team can answer from a laptop or a mobile, and a person working from home is on the same line as the desk they used to sit at. The switch-off is forcing a change you'd probably have wanted anyway.

That's the thinking behind a modern business phone system: a business line that lives wherever your team does, reachable in a keystroke, with none of the bloat the old systems carried. You don't get a new piece of hardware to mount on a wall. You get your number, working everywhere, out of the way until you need it.

So treat the deadline as a prompt, not a threat. Map your lines, protect the safety-critical kit, and pick a way of calling that you'll actually be glad to keep. The old network is going. What replaces it can be better.

If you'd like to be calling the modern way well before the lines go dark, you can join the Olatti waitlist and we'll bring you in early.