In 2027, BT is switching off the Public Switched Telephone Network — the traditional copper phone network that has carried calls in the UK for over a century. If your business still uses traditional landlines, ISDN or ADSL broadband, this affects you directly.
What is the PSTN switch-off?
The PSTN is the old analogue and digital phone network. Most business phone lines, fax machines, door entry systems, alarm diallers and ADSL broadband connections run over it. By January 2027, BT Openreach will have decommissioned the entire network — and anything that relies on it will stop working.
This isn't a gradual phaseout. It's a hard deadline.
What stops working on that date?
- Traditional landline phone numbers (01, 02 numbers on copper lines)
- ISDN2 and ISDN30 circuits used by many business phone systems
- ADSL and FTTC broadband connections that rely on the copper voice line
- Fax machines (unless using an internet-based fax service)
- Alarm systems and CCTV that dial out over a phone line
- Door entry and access control systems with phone line connectivity
- Lifts and building management systems with emergency phone lines
The last four catch a lot of businesses by surprise. If anything in your building dials out over a phone line for safety or monitoring purposes, it needs attention before 2027.
Why act now rather than wait?
The closer you get to 2027, the more congested the migration market becomes. Telecoms providers will be overwhelmed with last-minute moves, lead times will stretch, and prices will rise. Businesses that migrate early get better pricing, more choice, and a smooth transition rather than a rushed one under pressure.
There's also a practical benefit: modern VoIP phone systems are significantly better than the systems they replace. Caller ID linked to your CRM, calls on any device, voicemail to email, call recording, hunt groups — features that cost thousands on old ISDN systems are standard and inexpensive on VoIP.
What to replace it with
The replacement for PSTN is VoIP — Voice over Internet Protocol. Calls travel over your internet connection rather than a phone line. You keep your existing numbers. Your team can take calls on desk phones, computers or mobile apps.
For broadband, ADSL and FTTC connections move to FTTP (full-fibre) or SOGEA — both of which don't require a phone line at all and are generally faster and more reliable than what they replace.
What to do next
Start by auditing what you have. Count your phone lines, check your alarm system, check your lift, check any devices that might dial out. Then talk to a telecoms provider about a migration plan — one that covers everything, not just the phones.
We've been helping businesses migrate ahead of the switch-off since 2023. If you want a straightforward conversation about your specific setup, give us a call.