The Phone Line Switch-Off: What Small Businesses Need to Do

If your business still uses a traditional landline, it is going to change. The UK's traditional landline telephone network, the PSTN (Public Switched Telephone Network), is being retired, and calls are moving to internet-based technology, often called digital voice. This does not necessarily mean replacing your copper connection with full fibre. Digital voice can also run over copper-based broadband.

For many small businesses the change will be fairly quiet. The phone still rings and the number stays the same. But plenty of equipment besides the phone on the desk relies on a phone line, and that equipment is where problems tend to appear.

What is happening and when

BT and Openreach's PSTN retirement programme is currently due to finish on 31 January 2027. It was originally planned for December 2025 and was put back. Other operators run their own programmes, and your provider may move your lines before then, so the date that matters is the one your provider gives you. If you have not heard anything yet, do not assume nothing will happen to your lines.

Openreach has announced arrangements for lines that still have not moved by the deadline. Do not rely on them. They will not necessarily cover every type of line or device, and the details may change. If you want to know whether they could apply to you, ask your provider about eligibility and limitations.

ISDN is going too. Many older office phone systems use these digital lines, and they are being withdrawn as part of the move away from traditional telephone services. A phone system on ISDN needs as much attention as an ordinary landline.

Check the latest position with your provider and with Ofcom, which publishes guidance on the move to digital phone lines.

It is not just the phone

The devices most likely to cause trouble are the ones nobody thinks of as "the phone". Look out for:

• Intruder and fire alarms, including alarm diallers that call a monitoring centre or keyholder
• Card payment terminals that connect over a phone line
• Lift emergency phones
• Fax machines
• Franking machines that use the line to top up credit or report usage
• Door entry systems
• Some CCTV systems, particularly older ones that send alerts over a line
• Telecare devices, if your business provides or manages care
• Older phone systems (PBX) on analogue or ISDN lines

Some will carry on working unchanged. Others will need a setting changed, an adapter, or replacing. You cannot tell by looking, and your phone provider will not always know what is plugged in. Ask the supplier or maintainer of each device.

A plan you can follow

Start with an inventory and supplier checks, then work through the rest in order:

1. List every line. Your bills show the numbers. For each one, note what is plugged into it and where it is in the building.
2. Ask your provider when and how each line will move. Agree the cutover date, how long calls may be interrupted, whether an engineer is needed, whether your broadband needs upgrading and what equipment they will supply. Arrange temporary call diversion if you cannot afford to miss calls.
3. Contact the supplier of each device. Ask: will this work on a digital line, and if not, what do we need to do? Get the answer in writing for anything safety related.
4. Decide what to do about your phone system.
5. Arrange to keep your numbers.
6. Plan for power cuts and outages.
7. Test everything after the move.

Lines you no longer need can be cancelled. Before cancelling, check for linked services such as broadband, any numbers you want to keep, and contract or termination charges.

Be wary of anyone contacting you out of the blue about the switch-off who asks for payment or account details or pushes you to sign up quickly. Hang up and call your provider on a number you already know, such as the one on your bill.

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Your phone system and your numbers

If you have an older phone system, you can broadly retain it, adapt it or replace it. If it is reliable and the supplier confirms it is compatible, you may be able to keep it by connecting it over SIP trunks (internet-based lines) or through a suitable gateway. Alternatively, you could move to a hosted or cloud phone system using VoIP, where the provider runs the system and staff take calls on desk phones, computers or mobiles.

Either way, check how reliable your broadband is, whether it can handle the number of calls you make at once, and what happens to calls if the connection fails. Ask about backup connections and diverting calls to mobiles.

If you manage a cloud system online, protect the admin account with multi-factor authentication, keep handsets and software on supported versions, and ask about call barring or spending limits to stop unauthorised calls. The NCSC publishes practical security advice for small businesses.

Your numbers can normally come with you. Moving a number between providers is called porting. Ask the new provider to handle it, check which numbers are included, and do not cancel the old service until the port has gone through. Cancelling first can lose the number.

Power cuts, emergency calls and testing

Old copper phone lines carried their own power, so a basic phone kept working in a power cut. Digital voice does not. It relies on a router and other equipment that need mains electricity, so when the power goes, the line goes too unless you have planned for it.

For alarm diallers, lift phones, telecare devices and anyone who might need to call 999, that is a safety issue. Critical lines may need a battery backup unit. Ask your provider what they offer and how long it lasts, and ask device suppliers whether their equipment has its own backup or mobile fallback. Know the limits: a battery does not help if the broadband network itself is down, and mobile fallback needs adequate coverage where the device sits, plus its own tested power supply.

Ask your provider how 999 and 112 calls work on the new service and how your location is recorded and updated, particularly for staff using cloud phones away from the office.

Once a line has moved, test properly. Make and receive calls on every number, and check caller ID, hunt groups and voicemail. Arrange a test with your alarm monitoring centre, run a card payment, and check the lift phone, door entry, franking and CCTV. For power cuts, agree a mains failure test with your supplier covering the router, the fibre ONT if you have one, phone equipment and connected devices. Simply switching off the router can bypass the backup you are trying to test. Coordinate tests of monitored or safety-critical equipment with its maintainer.

Keep a note of what you tested and when, and report failures to the provider and device supplier straight away. Keep an eye on updates from your provider and Ofcom, since dates and arrangements may change.