PSTN switch-off 2027: what your UK business has to sort

If you run a business from a building that's older than your broadband, there's a cable in it you've never thought 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 decision from you. That's the problem, because the PSTN switch-off in 2027 turns that cable off, and sorting it is your job, not BT's.

In short: the PSTN switch-off ends the UK's old analogue phone network, ISDN included, by the end of January 2027. Calls move onto broadband instead. Phones are the easy part. The risk is the alarms, lift phones and card machines that dial out over copper without anyone noticing, and stop working the day those lines go dark.

I've seen the lines that are being switched off

I've sold and installed business phone systems since 2012, and back then that meant on-premise boxes running over ISDN for dentist surgeries, car garages and solicitors' firms. None of them had a comms room, so the system went under a desk or on the wall by the toilet, with the lines running into it and nobody looking at it again. Those are the lines Openreach is now turning off. The engineers at circle.cloud, the UK telecoms company I started in 2015 that installs and supports phone systems for small businesses, still install and support businesses like these, so I know what's still bolted to some of those walls. Most of it wasn't chosen because it was the best way to take calls. It came with the finance, and it stayed because nobody had a reason to look at it.

What does the PSTN switch-off in 2027 actually mean?

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

Openreach is retiring all of it and moving voice onto the internet. Your calls travel as data over broadband, the way your email already does. BT calls its consumer version "Digital Voice"; the general term is calling over the internet, or VoIP.

You can't opt out. It isn't a product being withdrawn, it's the network underneath the product going away. The only choice you get is whether you move on your own terms or have it done to you near the deadline.

The date that counts

You can't buy a new analogue or ISDN line any more. The national stop-sell came in back in 2023, so whatever you're running today is already 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 add up ordering kit, swapping devices over and testing the important things still work. A year goes quickly when the change touches your alarm, your lift and how you take payment.

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 on 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

One more thing, said 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, which means a power cut takes your line with it unless you've planned for backup. For a lift phone or an alarm, that isn't a detail. It'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.

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 it and whether 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; they'll have a switch-off plan and a part to play.
4. Decide how your actual calls should work. This is the moment to stop patching a setup someone leased to you years ago and choose something that fits how your team works now, 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

Two parts of the move are 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 phone side is the easy bit, if you let it be

At circle.cloud we've moved a lot of businesses off old lines and onto calls over the internet. It's routine when it's planned and painful when it's panicked, and the difference is usually whether someone walked round the building in the spring or in the January.

But I'd ask you to look at the phone part differently. Once your calls run over the internet, your number isn't tied to a socket in one building. You keep it, your team answers from a laptop or a mobile, and the 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 business line that lives wherever your team does: reachable in a keystroke, with none of the bulk the old systems carried. Nothing gets mounted on the wall by the toilet. 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 this time pick the way of calling you'd actually choose, rather than the one that came with the lease. The cable you never thought about is going. What replaces it can be the one thing in the building you did think about.

If you'd like to be calling the modern way well before the lines go dark, try for free (opens in a new tab).