What Is the PSTN Switch-Off? A Guide for Businesses

The PSTN switch-off is the planned shutdown of the UK's old copper telephone network, which carries traditional analogue and ISDN phone lines. Openreach will switch it off on 31 January 2027.

 

After that date, any business still running on an old phone line will lose the ability to make and receive calls. The good news is the fix is straightforward, and there is still time to move across calmly rather than in a rush.

 

What the PSTN actually is

 

PSTN stands for Public Switched Telephone Network. It is the copper-wire network that has carried UK phone calls for well over a century, from the first landlines through to the analogue and ISDN lines many businesses still use today.

 

In its place comes a fully digital system where calls travel over the internet instead of a copper circuit.

 

If your phone system plugs into a traditional line at the wall, whether that is a single analogue line in a small office or a multi-channel ISDN setup running 30 lines, it sits on the PSTN. That is what is going away.

 

When is the PSTN switch-off happening?

 

The firm national deadline is 31 January 2027.

 

It is worth knowing the history, because the date has moved before and some businesses have been told to ignore it as a result. The switch-off was originally set for December 2025, then pushed back to January 2027 to give telecare and vulnerable users more time to migrate safely. Openreach has since confirmed this date will not move again. As one senior Openreach manager put it, the network has reached a point where staying on it is riskier than moving off it.

 

The practical takeaway: do not wait for the deadline. A "stop-sell" is already in force across most of the country, which means you can no longer order new copper lines or make changes to existing ones in affected areas. New ISDN orders ended back in September 2023. Many telephone exchanges are also being migrated ahead of the final date as part of a phased rollout, so your lines could stop working before January 2027 depending on where you are.

 

What stops working when the line is switched off

 

This is the part that catches businesses out. The switch-off is not only about phone calls. Anything that quietly relies on an old phone line in the background will stop working too. That typically includes:

 

• Analogue and ISDN phone systems
• Card payment machines (PDQ terminals) that dial out over a phone line
• Door entry and intercom systems
• Lift emergency phones
• Some alarm and CCTV monitoring connections
• Older fax machines
• Broadband delivered over copper (ADSL and FTTC), which is being withdrawn on the same timeline

 

When the exchange serving your premises is switched off, these simply cease to function.

 

What replaces the PSTN

 

For phone calls, the replacement is VoIP, which stands for Voice over Internet Protocol. Instead of routing calls down a copper line, VoIP sends them over your broadband connection.

 

In day-to-day use it works exactly like a normal phone system, you still have desk handsets, extensions, call transfers and voicemail, but it runs on a newer, actively maintained network.

 

Most businesses moving across choose one of two routes:

 

Hosted VoIP or cloud-hosted PBX. Your phone system lives in the cloud rather than in a box in a cupboard. You get desk phones, a softphone app for laptops and mobiles, and a single system that works across multiple sites and remote workers. This is the most common choice for businesses replacing an ageing system outright.

 

Microsoft Teams as your phone system. If your team already lives in Teams, voice calling can be added so Teams becomes your business phone line, with proper external numbers for inbound and outbound calls. It is a tidy option for offices that have standardised on Microsoft 365.

 

The broadband side moves at the same time, typically to full fibre where it is available. Moving to a modern connection is also what makes VoIP reliable: with a stable broadband line, hosted systems deliver clear, consistent call quality, and many businesses find them more dependable than the copper lines they replace.

 

Will you keep your phone numbers?

 

Yes. This is the single biggest worry we hear, and the answer is reassuring. Your existing numbers can be ported (transferred) to the new VoIP system. There is no need to reprint stationery, update your signage or change the number on your website.

 

Number porting is handled by your new provider as part of the move and usually takes a couple of weeks to complete. The right approach is to get the new system working alongside the old one first, then port the numbers across once everything is tested, so there is no gap in service.

 

How to get your business ready

 

You do not need to do anything dramatic, but you do need a plan. The businesses that handle this well treat it as a straightforward project rather than an emergency. The order of work looks like this:

 

1. Audit what you have. Note every phone line, your current phone system, your broadband type, and crucially every piece of connected equipment, payment terminals, alarms, lift phones, door entry. This is the step most people skip and later regret.
2. Check your broadband. VoIP needs a stable connection. If you are still on copper broadband, a fibre upgrade usually happens as part of the same move.
3. Choose your replacement. Hosted VoIP, cloud PBX or Teams voice, sized to how your team actually works, including remote and multi-site staff.
4. Plan the number porting. Confirm which numbers move across and run the new system in parallel before you switch over.
5. Test, then go live. Check call quality, handsets, voicemail and any connected devices before retiring the old line.

 

Done in this order, the changeover is calm and there is no loss of service. Leave it until your exchange is days from switching off, and your options narrow considerably.

 

How CoreComms can help

 

We handle the whole move for businesses across the North West, West Yorkshire and beyond, from the first audit through to the day the new system goes live. That means surveying your current lines and connected equipment, recommending the right replacement for how your team works, managing the number porting so you keep your existing numbers, and being on hand for support afterwards.

 

With over seven years installing voice and data systems and a team carrying more than 50 years of combined experience, we are used to making this kind of changeover quietly and without fuss. We will translate the jargon into plain English, give you a clear plan, and make sure nothing important gets missed before the deadline.

 

If your business still runs on an old phone line, the sensible next step is a short conversation. Take a look at our business telephone systems, or talk to our team about getting ready for the switch-off in good time.