There is a date after which parts of your building simply stop working, and most UK organisations have not finished preparing for it. On 31 January 2027, Openreach permanently switches off the Public Switched Telephone Network — the copper infrastructure that has carried UK phone calls for over a century. Openreach has said there will be no “big bang” on 1 February and exchanges will go dark on their own schedule. That changes when your line dies, not whether it does — and migrating takes months, not days.
The government’s own guidance is unambiguous: every user of the Openreach PSTN must be migrated to a new service before that date. And the scale of what is left to do is equally clear — in February 2026 Openreach reported that more than half a million business lines still needed to be upgraded, including over 12,000 lift lines and around 500 lines serving CCTV networks.
This post sets out what actually stops working, why your phone bill is not a reliable guide to your exposure, and the sequence we recommend for migrating without disruption.
What stops working on 31 January 2027
The obvious casualties are the obvious ones: traditional analogue phone lines and ISDN2/ISDN30 circuits, including the ISDN trunks that connect many on-site PBX systems. If your phones run over ISDN today, that service ends entirely.
Less obvious, and more dangerous, is broadband. FTTC and ADSL connections are delivered over a copper phone line, and they die with the PSTN. Any business still on FTTC needs to move to FTTP or SOGEA — and in many areas the choice is already being made for them: where full fibre covers roughly 75% of an exchange, Openreach applies a stop-sell on new copper-based orders. As of February 2026 that stop-sell covered 1,281 exchanges and 12.5 million premises. Checking whether your site can still order what it currently runs is a five-minute job worth doing this week.
Then there is the category almost every migration plan misses on the first pass: devices that use a phone line without being phones.
- Lift emergency phones. Older lifts often use a PSTN-connected emergency line. Lift communications are a regulated safety system, not a convenience — a dead lift line is a compliance problem as well as an operational one.
- Intruder and fire alarm diallers. Many monitored alarms report to their receiving centre over a dedicated phone line. When the line dies, the alarm may still ring locally but stop reporting — and a monitored alarm that is not reporting can invalidate the insurance it exists to protect. Ask your alarm maintenance company what path your signalling uses, explicitly.
- Door entry and access control intercoms. Wired into a phone line in thousands of buildings, especially multi-tenant ones.
- Payment terminals. Older PDQ terminals that dial out over a landline. When they stop, revenue stops with them.
- CCTV with line-based monitoring, fax machines, EPOS and telecare devices. Each niche, each quietly dependent on copper.
A useful rule of thumb: if a device has a phone socket, it needs assessing.
Why your bill undercounts your exposure
The first instinct is to pull the telecoms bill and count the lines. Do that — but do not stop there. In practice, buildings regularly contain lines that appear on nobody’s bill the way you’d expect: alarm lines billed to a facilities contract, lift lines under a maintenance agreement, door-entry lines installed a decade ago and paid within a service charge. Openreach’s own advice amounts to “review your assets, and if you are unsure, ask” — because the people who know what is connected are rarely the people holding the bill.
This is the core of the problem, and it is why we recommend a physical audit rather than a paperwork one. Walk the building. Comms room first: count the lines and the equipment. Then the plant that never gets audited — lift motor rooms, alarm panels, door entry cabinets, payment terminals. The output should be a simple register: what is connected, what it depends on, what needs to happen to it, and by when. Fifteen undocumented lines in a typical small office building is not unusual.
Not sure what in your building still runs on copper?
Thirty minutes with an engineer, and you will know what your exposure looks like and which of it is urgent. No obligation.
Why leaving it late costs more — in money and in options
Three pressures are already visible.
Prices are rising on what remains. Openreach has been increasing wholesale prices on legacy copper products to push the final migration — with steps of +20% in April 2026 and +40% in each of July and October 2026 reported by ISPs. Staying on copper through the winter now means paying a premium for a service with an expiry date.
Engineers are booking out. A typical migration involves site work, number porting and testing. Number porting alone takes on the order of two weeks, and one rejected port request — a mismatched account detail — restarts the clock. Openreach and industry sources alike warn that engineering capacity tightens through the final quarter. Providers are already telling businesses that December 2026 is the latest comfortable start date; leave it beyond that and you are negotiating for remaining slots, not choosing them.
Some sites go dark before the national date. The January 2027 date is the national backstop. Individual exchanges are being migrated ahead of it as full fibre reaches them — so the effective deadline for a specific building can be earlier, and is rarely advertised to the people in the building.
The migration sequence that works
Every estate is different, but the order of operations is consistent:
- 1. Audit. Physical walk-through; register every line and every copper-dependent device, including the ones on third-party contracts. This is the step everything else depends on, and it is the one most often skipped.
- 2. Check the connectivity underneath. Voice-over-IP and IP-based devices run on your data network. That means the network has to be ready before anything migrates: enough bandwidth and the right kind (symmetric fibre for sites that need it), a router and switching that can prioritise voice traffic under load, and cabling that supports the new equipment. A phone system that shares a contended broadband line with everything else will tell you about it on its first busy Monday. If your LAN or WiFi was installed more than a few years ago, test it — don’t assume it. We covered what a proper survey involves in what a professional WiFi site survey actually involves.
- 3. Plan device-by-device. Phones to hosted VoIP or SIP. Alarm diallers to IP or 4G signalling modules — usually a modest cost via your alarm company. Lift lines to a compliant mobile or IP solution. Door entry, PDQ terminals and CCTV each get a named plan, a named owner, and a date.
- 4. Port numbers early. Porting queues lengthen as the deadline approaches, and errors restart the process. Porting in October is a routine; porting in January is a gamble.
- 5. Test before you rely. Migrate one site or one team first. Check call quality at 9am, not at 9pm. Test what happens to emergency calling, alarm reporting and door entry before the old line is ceased — and keep the old service overlapped until the new one has proven itself.
- 6. Cease properly. Cancel old lines formally once migrated. Billing on ceased copper services has a documented habit of continuing quietly if nobody closes it down.
Where we fit — and where we don’t
A point worth making plainly, because it will save you time: choosing your new telephony platform — the hosted VoIP provider, the SIP trunks, the licences — is your communications provider’s job, and the market there is deep and competitive. We are not that provider.
What we are is everything the migration stands on. The cabling that has to reach the new equipment. The switching and WiFi that have to carry voice with the same reliability they carried data. The segmentation that keeps a door-entry system or a building-management network from sitting on the same flat network as your servers. The audit that finds the lines nobody knew about, and the monitoring that tells you the day something in the new estate misbehaves rather than the week it surfaces. We have spent over 20 years designing, installing and managing exactly this layer across London and the South East.
If you are planning a migration and want the infrastructure underneath it checked properly — measured, not assumed — that is where we start.
We offer a free 30-minute infrastructure review for organisations in London and the South East. We look at what you are running, what it depends on, and where the switch-off risk sits. No obligation.
