In January 2027, the UK's old analogue phone network (the PSTN) will be switched off for good. Every business still relying on it will need to have moved to a modern, internet-based alternative before then. It's one of the biggest shifts in UK business communications in decades, and yet a surprising number of organisations either haven't heard about it or assume it's a problem for their future selves.
This guide explains what the switch-off is, why it matters, what happens if you do nothing, and the practical steps to prepare — in plain English, without the jargon.
What is the PSTN switch-off?
PSTN stands for the Public Switched Telephone Network: the traditional copper-line phone system that's carried the UK's calls for over a century. Alongside it sits ISDN (Integrated Services Digital Network), the digital upgrade many businesses use to run multi-line phone systems.
Both are being retired. Openreach, which owns and maintains the underlying network, is switching off the PSTN and ISDN and moving everything to digital, internet-based calling — technology known as VoIP (Voice over Internet Protocol) or all-IP. In practice, that means your phone calls will travel over your internet connection rather than a dedicated phone line.
The final switch-off date is 31 January 2027, and Openreach has confirmed there will be no further extensions.
Why is it happening?
The copper network is old, increasingly expensive to maintain, and no longer fit for how modern businesses communicate. Sourcing parts and engineers for decades-old infrastructure is getting harder and costlier every year.
Digital, internet-based calling is more reliable, more flexible, and packed with features the old network could never support — video, messaging, integration with the other tools your business already uses. The switch-off isn't just the end of something old; it's a move to something considerably better.
Why it matters sooner than you think
It's tempting to file "January 2027" under "deal with it later." Here's why that's a mistake.
Waiting is already getting expensive
Staying on the old network isn't a neutral choice. Openreach has been increasing wholesale prices on legacy lines in stages through 2026 — effectively doubling the cost of the old service in its final period, as a deliberate nudge to get businesses to move. Every month you delay, you're paying a premium for a network that's on its way out.
It's not only about phones
This is the part that catches businesses out. Anything that relies on a traditional phone line is affected — not just your handsets. That includes older broadband connections, fire and intruder alarms, lift emergency lines, door entry systems, and card payment terminals. A proper review of everything connected to a phone line should be part of any migration plan.
Migrations take planning, not panic
Moving your phone system properly — porting numbers, setting up call routing, training your team — takes a few weeks when done well. Leave it to the last minute, and you're rushing a business-critical system, which is exactly when things go wrong. The businesses that plan ahead will have a smooth transition; those that wait will be scrambling alongside everyone else in late 2026.
What happens if you do nothing?
If your lines haven't migrated by the deadline, they don't simply carry on as before. At best, they fall back to a stripped-down, emergency-only provision that won't support the features a business phone line needs. At worst, you lose the ability to make and receive calls on those lines entirely.
With millions of lines still to migrate across the UK — a significant share of them serving businesses — the closer we get to the deadline, the busier providers become. Acting early means you migrate on your own terms; leaving it late means joining the last-minute rush.
What are your options?
The good news is that preparing for the switch-off is also an opportunity to modernise your business's communication.
The main routes are:
Move to a VoIP phone system
A dedicated internet-based phone service replaces your old lines with internet-based calling — keeping your existing numbers while adding flexibility and features the old network couldn't offer.
Move your telephony into Microsoft Teams
If your business already uses Microsoft 365, one popular option is to use Microsoft Teams as your full business phone system. Calls, chat, video, and collaboration all live in one place; your team works from anywhere; and there's no separate phone system to maintain. For many SMEs already invested in Microsoft, it's the most natural and cost-effective route.
The right choice depends on how your business actually uses the phone, your existing setup, and your budget — which is exactly the kind of thing worth talking through with an IT partner who's done it before.
How to prepare: a simple checklist
- Audit what's connected to your phone lines: Phones, yes, but also alarms, broadband, payment terminals and door entry systems.
- Check your contract position: If you're mid-term on a phone system contract, factor in the timing of a switch.
- Assess your internet connection: Since calls will travel over it, a reliable, well-configured connection is the foundation. This is usually straightforward to check and fix.
- Choose your route: A standalone VoIP system, or Microsoft Teams telephony if you're already in the Microsoft ecosystem.
- Plan the migration: Number porting, call routing and team training, scheduled to avoid disruption.
- Don't leave it to 2026: The earlier you start, the smoother (and cheaper) the move.
Not sure where to start with the switch-off?
The PSTN switch-off is a deadline, but it's also a chance to modernise how your business communicates — done right, you come out the other side with a better, more flexible phone system, not just a compliant one. At Netitude, we help businesses across Somerset, Bristol and the Southwest plan and make the move without the headache. Get in touch for an honest conversation about your options.
Frequently asked questions
When is the PSTN switch-off?
The PSTN and ISDN networks will be switched off on 31 January 2027. After this date, traditional phone lines will no longer work, and all calls must be made over digital, internet-based connections.
What is the difference between PSTN and VoIP?
PSTN is the traditional phone network that carries calls over copper lines. VoIP (Voice over Internet Protocol) carries calls over the internet instead. The switch-off means businesses are moving from PSTN to VoIP-based systems.
Will the switch-off affect my broadband?
It can. Older broadband types that run over the copper network (such as ADSL and some FTTC connections) are affected by the switch-off. Part of preparing is making sure your connectivity is ready for an all-IP world.
Can I keep my existing phone numbers?
Yes. When you move to a modern phone system, your existing numbers are ported across, so customers and suppliers notice no change.
What's the best replacement for a small business?
It depends on your setup, but for businesses already using Microsoft 365, moving telephony into Microsoft Teams is often the most cost-effective and straightforward option — one platform for calls, chat, meetings and collaboration.
The PSTN switch-off isn't a reason to panic, but it is a reason to plan. The date is fixed, the old network is on its way out regardless, and staying put only gets more expensive the longer you leave it.
The takeaways are simple: know what's connected to your phone lines (it's rarely just the phones), understand that January 2027 is a hard deadline with no further extensions, and remember that acting early means moving on your own terms rather than joining the last-minute rush.
Handled properly, the switch-off is far more of an opportunity than an obligation: a chance to give your business a more flexible, more capable phone system that works wherever your people do. The businesses that come out of this best won't be the ones who waited until 2026; they'll be the ones who treated it as a planned upgrade, not an emergency.