Introduction
UK businesses face a major phone network change called the PSTN switch off. Old landline services will stop working completely. Digital phone systems will replace them instead.
This affects more than just desk phones. Card machines for payments, security alarms, and other socket-connected devices will also fail. Every business needs a digital phone replacement before the old network shuts down.
This guide explains simply what happens, when it happens, and your easy options to switch without problems.
What Is the PSTN Switch Off?
PSTN stands for Public Switched Telephone Network the copper wires that have carried UK phone calls for generations. Every traditional landline plugs into this ageing system. The PSTN switch off closes this network permanently. No more calls through phone sockets. Devices connect to internet routers instead, using digital voice over broadband.
Simply, old landlines get replaced by internet phone calls.
Why Is PSTN Being Switched Off?
Copper phone networks cost businesses far too much to maintain as cables age and fail more often. Spare parts disappeared years ago, and engineers who know the old systems become harder to find every year.
Today’s businesses need remote working, smart call routing, reports, and CRM connections that PSTN simply cannot provide. Digital voice over your existing broadband handles calls, data, and cloud apps together much more efficiently.
UK telecoms switch to digital because keeping decaying copper alive makes no business sense anymore.
BT Landline Switchover 2027 When Will PSTN End?
BT manages the PSTN shutdown step by step, so firms get plenty of notice. Come December 2025, you can’t buy, move, or upgrade any PSTN or ISDN lines anymore no more traditional landlines available.
Full BT landline switchover wraps up January 2027. That’s when PSTN goes dark for good. Anything still plugged into old lines simply stops working.
What Is the BT ISDN Switch Off?
ISDN handles several calls at once lots of older office phone setups still use it. Businesses keep main numbers on ISDN for solid call quality. BT shuts down ISDN with PSTN since both need the same copper wires. ISDN2 and ISDN30 go away completely. Firms must switch to digital phones before everything stops.
Which Business Services Are Affected?
The PSTN switch off affects more than desk phones. Any system connected to a phone socket may rely on PSTN, including:
- Office phone systems
- Card payment machines
- Alarm and security systems
- Fax machines
- Door entry and lift phones
If these services are not upgraded, they may stop working when PSTN is switched off meaning customers may not reach you, card payments could fail, and security systems may not be able to call for help.
What Will Replace PSTN?
PSTN gets replaced by digital voice over the internet better known as VoIP. Instead of plugging phones into wall sockets, they connect to your internet router or office network. Your existing phone numbers move across too, so customers keep dialling the same way they always have.
For most businesses, the switch feels seamless calls ring normally and customers notice nothing different. Behind the scenes though, everything runs more reliably with better remote working support and modern features like call queues or voicemail that were never possible before.
PSTN Replacement Options for Businesses
Different businesses need different PSTN replacements. A five person team, high street retailer, or call centre each require tailored solutions.
VoIP phone systems work best for small/medium firms plug into any device with routing, voicemail, mobile apps included.
Cloud PBX swaps traditional office phones without hardware installs.
Microsoft Teams Phone builds calls into Teams for Microsoft 365 users.
SIP systems update ISDN while keeping current handsets.
See which phone system fits your business
VoIP vs Digital Phone Lines
Digital lines act like old landlines but run over the internet perfect for basic needs.
VoIP/cloud platforms add mobile access, call queues, reports, multi-site routing. Most businesses find VoIP delivers better value and adaptability.
What Happens If You Do Nothing?
When the PSTN network shuts down, any business still using traditional phone lines loses phone service completely. Customers hear “number not in service” when calling, staff cannot dial out, and payment card machines fail to authorise transactions.
Security alarms and monitoring systems stop sending alerts to response centres. Elevator phones and door entry systems go silent. All these services plug into the same dying copper network.
Waiting until the deadline creates chaos limited providers charge premium rates, rushed installations fail, and businesses lose days or weeks of operation. Early planning avoids these costly disruptions entirely.
How to Prepare for the PSTN Switch Off
Step 1: Find everything using phone sockets
Check desk phones, card machines, alarms, door entry systems anything plugging into wall phone sockets. Call your alarm company and payment provider to confirm if they use PSTN/ISDN lines.
Step 2: Match the right phone system to your business
Compare VoIP, cloud PBX, digital voice by user numbers, call volume, remote working needs. Early switching lets you test everything, move numbers smoothly, train staff properly.
Step 3: Switch before deadline chaos
Moving now avoids rushed installs, high prices, service gaps. Test period ensures everything works perfectly before PSTN shuts down for good.
Check your best VoIP alternatives
FAQ
1. What is the PSTN switch off?
The PSTN switch off is the UK’s move from copper landline phone services to digital voice over the internet. It means traditional phone lines will no longer carry calls. Businesses must switch to a PSTN replacement to keep their phones working.
2. When is the BT landline switchover?
The BT landline switchover 2027 is when all PSTN services will be fully turned off across the UK. From January 2027, no calls will run on copper phone lines. Any business still using PSTN will lose service.
3. What is the BT ISDN switch off?
The BT ISDN switch off is the closure of ISDN2 and ISDN30 business phone lines. These services use the same old network as PSTN and will stop working at the same time. Businesses using ISDN must move to digital phone systems.
4. What will replace PSTN for businesses?
PSTN is being replaced by digital voice services such as VoIP, cloud PBX and Microsoft Teams Phone. These use broadband or fibre instead of phone lines. They also support modern features like call routing and mobile apps.
5. What should businesses do now about the PSTN switch off?
Businesses should review every service that uses a phone socket and identify anything still running on PSTN or ISDN. Comparing PSTN replacement options early avoids last-minute disruption. Planning ahead ensures a smooth move to digital calling.
Conclusion
The PSTN switch off is permanently ending traditional landlines in the UK, and with the BT landline switchover 2027 and BT ISDN switch off approaching, every business must move to a digital phone system. Choosing the right PSTN replacement protects customer calls, payments and daily operations while giving businesses a modern, flexible way to communicate in the future.
See your PSTN replacement choices
