Key takeaways
- The PSTN and ISDN switch off is due to conclude on 31 January 2027, less than four months away.
- It affects more than phones: alarms, lift lines, card machines, franking machines, door entry and fax can all rely on copper lines.
- You can normally keep your existing phone numbers when you move to VoIP.
- Openreach has set out a temporary, limited and more expensive fallback for unmigrated lines; it is not a plan.
- Audit every line now, test equipment on a digital line and book your move early.
For decades, UK business phone lines have run over the public switched telephone network, or PSTN: the copper network that carries traditional analogue calls. ISDN, the digital version many businesses used for multi line phone systems, runs over the same old infrastructure. Both are being retired. The switch off was originally planned for the end of 2025, was pushed back, and is now due to conclude on 31 January 2027. With less than four months to go, any business still relying on these lines should be acting now.
What is happening and when
Openreach, which runs most of the UK's phone network, is withdrawing its Wholesale Line Rental products, and BT is retiring the PSTN that sits behind them. In its reporting on Openreach's plans in September 2026, ISPreview confirmed that the switch off is currently due to reach its conclusion on 31 January 2027, and that migration orders must be placed by that date.
Openreach has also set out what happens to single lines that have not moved by then. Rather than an immediate hard disconnection, a temporary service called Emergency Voice Access will keep a basic line running for essential calls. Openreach describes it as temporary, limited and more expensive than modern alternatives, and ISPreview reports that Openreach's message is that "no one should wait for the PSTN to close before upgrading". It is a safety net, not a destination, and it does not help multi line ISDN phone systems.
New PSTN and ISDN lines have not been available for some time in most areas, and the prices providers pay for legacy lines have been rising, so staying put is becoming more expensive anyway.
What equipment is affected
The obvious item is your phones. The less obvious ones are the devices that quietly use a phone line to send signals. These are the items most often missed, and some of them are safety critical.
| Equipment | Why it matters | What to do |
|---|---|---|
| Office phone system on ISDN or analogue lines | Calls in and out stop working | Move to a hosted VoIP system or SIP trunks |
| Intruder and fire alarms with a monitored line | Alarm signals may not reach the monitoring centre | Ask your alarm company to confirm compatibility or fit a digital or mobile signalling unit |
| Lift emergency phones | A trapped passenger may not be able to call for help | Speak to your lift maintenance company about a digital or mobile solution |
| Card payment terminals on a phone line | You may be unable to take card payments | Move to a terminal that uses broadband, WiFi or mobile data |
| Franking machines | Postage credit and updates may fail | Check with your supplier; many newer models use the internet |
| Fax machines | Traditional fax over analogue lines is unreliable on digital services | Move to email or an online fax service |
| Door entry, gate and barrier systems | Visitors may be unable to call through | Check with the installer for a digital or mobile option |
| Telecare, building management and remote monitoring units | Alerts may not get through | Contact the supplier and test on a digital line |
Many of these devices can work on the new digital services with an adapter or an update, but some cannot. The only way to know is to check with each supplier and test.
Moving to VoIP: what it means
VoIP, short for voice over internet protocol, carries calls over your internet connection rather than the old copper network. For businesses, it usually means one of two things:
- Hosted VoIP or cloud phone system: your phone system lives in the cloud. Staff use desk phones, a softphone app on their computer or an app on their mobile. Calls can ring in the office, at home or on the move, and features like call queues, recordings and voicemail to email are built in.
- SIP trunks: if you have a newer on premises phone system that you want to keep, SIP trunks replace ISDN lines with internet based ones.
For most small and medium sized businesses, a hosted system is simpler, more flexible for hybrid working and removes the need to maintain a phone system in a cupboard. Because calls now depend on your internet connection, a good connection matters. Our guide to full fibre and leased lines covers your options, and a backup connection or the ability to divert calls to mobiles keeps you reachable if the line drops.
Keeping your phone numbers
You can normally keep your existing phone numbers when you move to VoIP. The process is called porting. Your new provider requests the transfer from your old one, and on the agreed day calls start arriving on the new system. A few practical points:
- Find a recent bill for every line so you have the exact numbers, account details and who the line is with.
- Do not cancel your old lines before the port completes, or you risk losing the numbers.
- Allow time. Porting is usually straightforward, but complex ISDN number ranges can take longer, and providers are expected to be busy as the deadline approaches.
- Check for contract end dates and early termination charges on your existing lines.
Your PSTN switch off action plan
- List every line. Go through your phone bills and look for every number, including lines you have forgotten about that only serve an alarm or a lift.
- Trace what is plugged into each one. Walk round the building: phone system, alarm panel, lift, card machine, franking machine, fax, door entry.
- Contact each equipment supplier. Ask in writing whether their device works on a digital line and what they recommend.
- Check your internet connection. Make sure it can carry your calls reliably, and consider a backup.
- Choose your phone solution and agree a porting date.
- Test before you rely on it. Especially alarms, lift lines and payment terminals.
- Cancel old lines only once everything has moved and been tested.
How Cyber Fits can help
Our sister company Virtual Voice Office provides hosted business VoIP phone systems, handsets and number porting for businesses across the UK, and can be reached on 0191 543 3488 or at virtualvoice.uk/business. As your IT provider, Cyber Fits can help with the audit, the network and WiFi side, and making sure your broadband is up to the job. Find out more on our business phones page, or book a free IT review and we will help you list what needs to move before the deadline.
Frequently asked questions
When is the UK PSTN switch off?
The withdrawal of the old analogue phone network and related wholesale line products is currently due to conclude on 31 January 2027, following an earlier plan for the end of 2025.
Will my business phone line just stop working on 31 January 2027?
Openreach has set out a temporary Emergency Voice Access service for single lines that have not moved, but it is limited, more expensive and not intended as a long term option. Multi line ISDN systems and connected equipment should be moved well before the deadline.
Can I keep my phone number when moving to VoIP?
Yes, in most cases. Your new provider ports the number from your current provider. Keep your old lines active until the port has completed.
Does the switch off affect alarms and card machines?
It can. Any device that uses a traditional phone line, including monitored alarms, lift emergency phones, card terminals, franking machines and fax, needs checking with its supplier and testing on a digital service.
Our guides are written by the team who support businesses across the North East every day. If anything here raises a question about your own setup, ask us.