The PSTN & ISDN Switch-Off: What UK Small Businesses Must Do Before the Deadline

In short

The UK's analogue phone network (PSTN) and its digital cousin ISDN are being retired. Traditional phone lines will stop working and everything moves to internet-based calling (VoIP). This guide explains what's changing, who's affected, why waiting is risky, and how to switch smoothly, including keeping your existing phone number.

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The UK’s old phone network is being switched off

For over a century, UK phone calls have travelled over the Public Switched Telephone Network, or PSTN. It’s the analogue system behind the traditional landline in most offices, shops and reception desks. ISDN is its slightly newer digital relative, used by businesses for multiple lines and features.

Both are being retired. Openreach, which runs most of the UK’s underlying network, is moving everyone to internet-based calling. The old copper phone lines will stop carrying voice, and calls will run over broadband instead, using a technology called VoIP (Voice over Internet Protocol).

This isn’t optional and it isn’t a sales gimmick. It’s a national infrastructure change, and every business still using an analogue or ISDN line will need to move.

What is actually changing

In plain terms:

PSTN (analogue lines) are being switched off. The socket on your wall that a normal phone plugs into will no longer work for calls.
ISDN is going the same way. If you have a phone system with several lines and an ISDN circuit, that’s affected too.
VoIP replaces both. Your calls travel over your internet connection instead of a dedicated phone line.

The original nationwide switch-off date was December 2025. That has moved to the end of January 2027, partly to protect vulnerable users who rely on analogue services. But the direction of travel is fixed: you can no longer buy new analogue or ISDN lines in most areas, and exchanges are already being migrated across the country.

This isn’t optional and it isn’t a sales gimmick. It’s a national infrastructure change, and every business still using an analogue or ISDN line will need to move.

Why you shouldn’t wait until 2027

It’s tempting to file this under “deal with it later”. Here’s why that’s a mistake.

Your exchange may migrate before the national deadline. The 2027 date is a backstop. Many areas are switching earlier, and once your local exchange goes, your line goes with it.

Porting takes time. Moving your existing phone number to a VoIP provider isn’t instant. It usually takes a few working days, and doing it under pressure, days before a cut-off, is how businesses end up temporarily unreachable.

Hidden devices need checking. Alarms, lift phones, door entry systems and card machines often quietly rely on an analogue line. Discovering that during a rushed migration is stressful and can leave you non-compliant on safety.

Switching now is cheaper and calmer. Doing it on your timeline lets you plan, test and train staff. Doing it in a panic rarely goes well.

The upside: VoIP is genuinely better

This is one of those rare forced changes that actually improves things. Modern VoIP gives a small business features that used to cost a fortune:

Take calls anywhere. Your business number rings on a desk phone, laptop or mobile app, so staff can work from home or on the road without giving out personal numbers.
Easy to scale. Adding or removing a line is a setting, not an engineer visit.
Better call handling. Menus, hunt groups, voicemail-to-email and call recording come as standard on most plans.
Lower running costs. Line rental disappears and call charges are typically lower, especially for multi-site businesses.
One less thing to maintain. No ageing on-premise phone system to nurse along.

How to switch, step by step

You don’t need to be technical to get this right. Follow a clear process.

1. List everything on a phone line

Walk the building. Note every device connected to a phone socket: handsets, the main phone system, fax, card machines, alarm panels, lift emergency phones, door entry, even the postage franking machine. This list drives everything else.

2. Check your internet

VoIP calls need a stable connection, not necessarily a fast one. If your broadband drops out regularly, sort that first, or plan for a backup connection so calls don’t fail.

3. Choose a VoIP provider

Look for clear UK pricing, number porting included, a proper mobile app, and support you can actually reach. For most small businesses we recommend AirLandline, a UK VoIP and virtual landline service that keeps things simple: your existing number, calls on any device, and no complicated hardware to buy.

4. Port your number

Ask your new provider to port your existing business number across. You keep the number customers already know. Start this early, as it’s the step with the longest lead time.

5. Sort the non-phone devices

For every alarm, lift line or card machine on your list, contact its supplier and ask what they recommend for a digital line. Some work fine over VoIP, some need an alternative, and safety-critical ones (like lift emergency phones) must never be left to chance.

6. Test, then train

Run the new system alongside the old one if you can. Check calls in and out, voicemail, and call forwarding for power cuts. Show staff the app and the basics. Then retire the old lines.

Don’t forget power and resilience

One genuine trade-off: analogue phones worked in a power cut because they drew power from the line. VoIP needs mains electricity and internet, so both stop in an outage.

The fix is straightforward. Set up automatic call forwarding to a mobile, which most VoIP services do out of the box, so calls reach you even if the office goes dark. For sites where phones are critical, add a battery backup (UPS) for the router and, ideally, a mobile data failover.

Getting this off your plate

The switch-off is a hard deadline, but the migration itself is manageable with a bit of planning. The businesses that struggle are the ones that leave it to the last few weeks and discover an alarm or card machine that won’t cooperate.

If you’d rather not manage the audit, porting and testing yourself, this is exactly the kind of change a managed IT provider handles day to day. We can review what you’ve got, plan the move around your working hours, and make sure nothing important goes quiet. Take a look at our IT services and transparent pricing, or get in touch for a straightforward chat about your lines before the deadline creeps up.

The old network is going. Moving now, on your own terms, turns a looming problem into a genuine upgrade.

Frequently asked questions

When exactly is the switch-off happening?

Openreach originally set a nationwide date of December 2025, which has since moved to the end of January 2027. Some exchanges are already migrating and selling of new analogue and ISDN lines has largely stopped. Because timings vary by area and provider, treat 2027 as a hard backstop, not a target, and switch well before then.

Will my business lose its phone number?

No. Your existing number can almost always be ported (transferred) to a VoIP provider, so customers reach you exactly as before. Start the process early, as porting can take a few working days and occasionally longer for numbers held by certain providers.

What happens to things like alarms, lifts and card machines on the old lines?

Anything plugged into an analogue line, such as alarm systems, lift emergency phones, door entry, PDQ card machines and some fax setups, may need reconfiguring or replacing. Make a list of every device on a phone line now and check each one with its supplier before you migrate.

Do I need faster broadband for VoIP to work?

Not necessarily. Voice calls use very little bandwidth. A stable connection matters more than a fast one. Most modern business broadband handles VoIP comfortably, but if your internet drops out often, fix that first or add a backup connection so calls stay reliable.

What if there's a power cut? Old phones still worked.

True. Analogue phones drew power from the line itself. VoIP handsets need mains power and internet, so both stop in an outage. The practical fix is call forwarding to a mobile, which most VoIP services do automatically, plus a battery backup for critical sites.

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