The UK’s old copper phone network, known as the PSTN, is being switched off. BT and Openreach have set 31 January 2027 as the date by which traditional phone lines, ISDN and the older broadband that relies on them must move to digital services, and Openreach says there is no extension to the deadline. If your business still has a traditional line, or anything plugged into one such as an alarm, a lift phone or a card machine, the time to act is now rather than in January.
The short answer
- The date: 31 January 2027 for lines on the BT and Openreach network. Other networks, including Virgin Media O2, also plan to retire their old landlines, but Ofcom says their dates haven’t been set yet.
- What’s affected: traditional analogue lines, ISDN lines used by older office phone systems, and broadband that runs over the old line (ADSL).
- The hidden risk is equipment that uses a phone line without anyone thinking of it as a phone: alarms, lift phones, card machines, franking machines, fax, door entry and CCTV.
- What to do: find every line, ask each equipment supplier whether their kit works on a digital line, and talk to your phone provider about moving.
What’s being switched off, and why
The PSTN has carried phone calls for decades. Ofcom says the technology is beyond its intended lifespan and becoming increasingly unreliable, which is why BT is retiring it. In its place, calls run over a broadband connection, either through a digital phone line or a cloud phone system.
BT’s guidance for business customers lists what’s being withdrawn: PSTN lines, ISDN (which many older office phone systems use), ADSL broadband and related services. Openreach says every service that relies on ISDN must move to an internet-based service by January 2027 or it will be ceased. At the end of July 2026, Openreach said around 1.5 million lines were still on the old network, including around 350,000 business premises.
What happens if you do nothing
Openreach’s guidance to businesses is direct: if your line hasn’t moved, you may be put onto a temporary emergency voice-only service, or you may lose your service altogether. Its briefing to phone companies adds that old lines left after the deadline keep being billed until they’re ceased, at higher wholesale prices from 1 February 2027, and that lines which can’t be moved will be ceased in stages.
Openreach also says only a limited set of calling features remains on the emergency service. Don’t count on it for anything else plugged into the line.
Equipment to check
The phones on your desks are usually the easy part. Problems come from equipment that quietly uses a phone line to call out or send data. Openreach and BT both name these as needing checks:
- Intruder and fire alarms that call a monitoring centre over the phone line.
- Lift emergency phones. BT says a standard digital line isn’t suitable for a lift line, so speak to your lift maintenance company.
- Card machines. Many already use broadband or a mobile signal, but BT says some still need a traditional line.
- Franking machines, which BT lists among older third-party products to check before you change your line.
- Fax machines, if you still have one. Many businesses replace fax with email at this point.
- Door entry, gate and CCTV systems that report or call out over the line.
- Older office phone systems connected by ISDN.
Some of this kit just needs reconfiguring and some needs replacing. Ofcom points out that certain features of the old network, such as the line supplying its own power, aren’t always replicated by digital services, which is why older alarm and monitoring equipment can stop working.
Power cuts
A digital line depends on your router, so it won’t work in a power cut unless there’s battery backup. Ofcom requires phone companies to offer customers who depend on their landline to call the emergency services at least one solution, such as a battery backup unit, that keeps them able to call for at least an hour. Ofcom expects few businesses to rely on their office line in this way, but gives a sole trader working from home and a small office with no mobile signal as examples where that protection is likely to be needed. For everyone else, a charged mobile phone and a small battery backup for the router are sensible.
What to do now
- Find every line. Your phone bill lists the numbers you pay for. Then walk round the building and note anything plugged into a phone socket, including the alarm panel, the lift, the comms cabinet and reception.
- Ask each supplier three questions. Does this work on a digital line? What will it cost to change? How long will it take? Openreach recommends asking equipment suppliers about compatibility, costs and timescales.
- Speak to your phone or broadband provider. They arrange the move for you. If you have a phone line but no broadband, ask what digital option they offer.
- Check your broadband. If you’re still on ADSL, it has to change anyway, so it’s a good moment to make sure your connection is fast and reliable enough for calls.
- Decide on your phone system. If you’re on ISDN, this is the time to move to a cloud or internet-based phone system. Ask your provider to confirm you can keep your existing numbers.
- Leave time. Some changes need an engineer visit or new equipment, and alarm or lift work may need booking in advance. Don’t leave it until January.
How we can help
We help businesses with their office phone systems, working alongside our telecoms partners. If we already look after your IT, we can help you find what’s connected to your lines, work with your equipment suppliers, and make sure your broadband, network and Wi-Fi are ready for calls to run over them. If the switch is part of a bigger change, such as an office move or refit, we can plan it as part of the project.
If you’re not sure what your business still has on the old network, book a call or ring us on 02920 022100 and we’ll help you work it out.
Sources
- Switch your business phone line to digital, Openreach.
- Openreach warns businesses: just six months left before the UK’s old phone network is switched off, Openreach, 31 July 2026.
- Industry briefing GEN06826 on arrangements after 31 January 2027, Openreach.
- The PSTN, ISDN and ADSL switch off: what it means for you, BT Business.
- Full fibre broadband: frequently asked questions, BT Business.
- Your landline is going digital: what you need to know, Ofcom, updated 26 August 2026.
- PSTN switch off and migration to Voice over IP, Ofcom letter to providers, 29 January 2026.