VoIP & Communications

The PSTN switch-off: what UK businesses must do before January 2027

The UK PSTN and ISDN switch-off is now 31 January 2027. What stops working, from lines to alarms, lifts, card terminals and fax, plus a migration checklist.

By Dig IT SolutionsUpdated 8 September 20267 min read

Short answer

The UK PSTN switch-off is the withdrawal of the analogue and ISDN telephone network, rescheduled to 31 January 2027. Every phone line, alarm, lift phone, card terminal, fax and door entry system using those lines will stop working. Businesses need to audit what depends on them, move to VoIP, migrate connected devices and port numbers in time.

The traditional telephone network that has carried UK landline calls for decades is being switched off. The date, after a postponement, is 31 January 2027. For most businesses the phones themselves are the easy part. The harder part is everything else quietly plugged into a phone socket: the alarm, the lift, the card terminal, the fax, the door entry panel. This guide sets out what is happening, what stops working, and a checklist to get through it without a scramble in late 2026.

What is being switched off

The public switched telephone network (PSTN) is the analogue copper network connecting premises to local exchanges. ISDN2 and ISDN30, the digital business lines that feed most on-site PBXs, run over the same infrastructure. Openreach is retiring all of it and moving voice to internet-based (IP) services.

Key dates:

September 2023: Openreach stopped selling new PSTN and ISDN lines in most of the UK ("stop sell"). Businesses opening a site since then have already been pointed at digital alternatives.
December 2025: the original switch-off date, now abandoned.
31 January 2027: the rescheduled date for withdrawal of the PSTN and ISDN.

Ofcom's guidance on moving landline phones to digital technology explains the change from the customer's side, including the protections providers must offer people who rely on a landline.

What stops working

Anything that uses an analogue line or an ISDN circuit. In a typical SME that includes:

Item	Why it is affected	Replacement
Phone lines and ISDN to the PBX	The line itself is withdrawn	Hosted VoIP, or SIP trunks to a recent PBX
Broadband over a phone line (ADSL, FTTC)	Rides on the withdrawn line	SoGEA or FTTP full fibre
Monitored intruder and fire alarms	Panel dials the receiving centre over PSTN	IP or mobile-network communicator, usually dual-path
Lift emergency phones	Autodialler on a PSTN line, legally required	Mobile-network or IP lift unit with battery backup
Card payment terminals	Older terminals dial over PSTN	Ethernet, Wi-Fi or mobile-network terminals
Fax machines	Analogue only, fax over IP unreliable	Email, scan-to-email, or a fax-to-email service
Door entry and gate intercoms	Autodial to a phone line	IP or mobile-network intercom
Telecare and lone worker devices	PSTN autodiallers	Mobile-network or IP equivalents
Franking machines and older EPOS	Dial-up over PSTN	Ethernet-connected models
Building management and metering	Dial-up modems	IP or mobile-network gateways

The phones are one line on that list. The rest are the items that cause the problems, because nobody remembers they exist until they fail.

Phones: moving to VoIP

For calls, the replacement is a hosted VoIP platform. The phone system moves to the provider's data centres, staff use IP desk phones and apps, and calls travel over your broadband. Dig IT deploys 8x8 through its VoIP and business phone systems service, and the comparison with the old network is in PSTN vs VoIP.

Two points matter for timing. Your network has to be ready: a business-grade connection, a router with quality of service, tested cabling and a 4G or 5G backup where phones are critical. And your numbers have to be ported, which is the step with the longest lead time. Both are covered in how to switch from a landline to VoIP.

Number porting: port before you cease

Every business wants to keep its numbers, and every business can, provided it does things in the right order. The new provider submits the port, the losing provider validates it against its records, a date is agreed and on that date calls arrive on the new platform. Only then should the old lines be ceased.

Cancelling a line first, whether by ending a contract, moving broadband or accepting a provider's "upgrade", can lose the number. If your broadband provider offers to migrate you to SoGEA, ask what happens to the voice number on that line before agreeing.

Broadband: SoGEA and FTTP

Broadband that was delivered over a phone line needs a new footing. SoGEA (single order generic Ethernet access) is fibre-to-the-cabinet broadband supplied without a voice line, on the same copper for the last stretch. FTTP is full fibre to the premises and, where available, the better choice for a business running phones and cloud services. Either way, treat the migration as a chance to check that the connection is business grade, with a service level and enough headroom for VoIP at the busiest time of day.

Alarms, lifts, terminals and the rest

Each of these has its own supplier, its own lead time and, in some cases, its own regulation.

Alarms. Talk to your alarm company about the communicator. Most will move you to a dual-path IP and mobile-network unit. Confirm with the alarm receiving centre and your insurer, because an alarm that has stopped signalling can affect cover.

Lifts. Emergency communication is a legal requirement. Your lift contractor will fit a mobile-network or IP unit with battery backup. Lead times can be months and every lift needs a test call.

Card terminals. Your payment provider can tell you which terminals dial over PSTN. Replace those with IP or mobile-network models.

Fax. Almost every business can retire it. For the few that cannot, a fax-to-email service or a scan-to-email workflow replaces the machine.

Door entry, intercoms, telecare, franking, metering. Ask each supplier the same question: does this dial over a phone line, and what is the replacement?

Where an existing alarm or intercom system is being replaced anyway, it can be worth folding it into a wider CCTV and physical security review rather than swapping like for like.

Power cuts and emergency calls

Analogue phones drew power from the exchange and worked in a power cut. VoIP phones do not, unless the network equipment is on a UPS, and staff move to the mobile app when the office loses power. Ofcom expects providers to offer customers who depend on a landline a solution, such as a battery back-up unit, that keeps access to emergency services for a period during an outage. For a business with lifts, alarms or lone workers, design the mobile-network fallback in from the start rather than assuming the broadband will always be there. Details of failover design are in is VoIP reliable for business calls.

A realistic timeline

When	What
Now	Audit every line, number, ISDN channel and device that uses a phone socket. Check contract end dates.
Within 3 months	Choose the VoIP platform, order any broadband upgrade, brief the alarm, lift and payment suppliers.
3 to 6 months	Network readiness work, submit number ports, replace connected devices as suppliers deliver.
6 to 9 months	Build and test the phone platform, run in parallel, cut over, cease old lines after ports complete.
Before autumn 2026	Everything migrated, tested and documented, with margin before demand for engineers peaks.

Leaving it to the final quarter of 2026 means competing with every other late business for porting slots, lift engineers and terminals.

The switch-off checklist

List every phone number the business owns, including fax, DDIs and non-geographic numbers.
List every line and ISDN circuit and what is connected to it.
Walk the building: alarm panel, lift, card terminals, fax, door entry, franking machine, anything with a phone cable.
Ask each device supplier what the replacement is and the lead time.
Confirm how broadband is delivered and what it will move to.
Assess the network at each site for VoIP: connection, router QoS, cabling, PoE, UPS, 4G backup.
Choose the hosted platform, handsets and apps.
Submit number ports. Do not cease anything until they complete.
Build, test and run in parallel. Test failover and 999 registered addresses.
Cut over, cease old lines, check the first invoice for lines that survived.
Update the continuity plan with the new phone divert procedure.

What to do next

If you have not yet audited what depends on your phone lines, that is the first job and it takes half a day. Dig IT runs the whole migration for businesses across Hertfordshire, west Essex and London, from the audit through network readiness, 8x8 deployment and porting to the alarm and lift suppliers. Talk to an engineer and we will map your timeline to the January 2027 deadline.

Frequently asked questions

When exactly is the PSTN switch-off?

BT and Openreach have rescheduled the withdrawal of the public switched telephone network and ISDN to 31 January 2027, having originally planned December 2025. New analogue lines and ISDN circuits have not been sold in most areas since September 2023. Ofcom's guidance on moving landlines to digital technology sets out what customers should expect from providers during the migration.

Will my broadband stop working too?

Broadband delivered over a phone line (ADSL and FTTC) is affected because the line it rides on is being withdrawn. The replacements are SoGEA, which is the same fibre-to-the-cabinet broadband without a voice line, and FTTP full fibre. Your provider will migrate you, but check the timing and make sure the new connection is business grade with enough capacity for VoIP.

What happens to our alarm if we do nothing?

A monitored intruder or fire alarm that signals over a PSTN line will stop reporting to the alarm receiving centre when the line ceases, even though the panel still sounds locally. You may not be told it has failed. Talk to your alarm company about an IP, mobile-network or dual-path communicator well before the deadline, and confirm the change with the monitoring centre and your insurer.

Do we need to replace our card terminals?

Only those that dial over a phone line. Many older countertop terminals do, and they will stop authorising payments when the line ceases. Terminals that connect over Ethernet, Wi-Fi or a mobile network are unaffected. Your payment provider can tell you which you have. Order replacements early, because demand for engineers and terminals will rise as the deadline approaches.

Can we keep our phone numbers?

Yes. Number porting to a VoIP platform is standard and providers are obliged to support it. Your main numbers, direct dials and non-geographic numbers all move. The one rule is to port before you cease: a line cancelled before the port completes usually takes its number with it. Allow a few weeks for straightforward ports and longer for ISDN30 ranges.

What about lift emergency phones?

Lift emergency phones are typically autodiallers on a PSTN line and are a regulatory requirement, so they must keep working. Replace the dialler with a mobile-network or IP unit that meets the lift standard and has battery backup. Lift maintenance contractors handle this, but lead times can be long and each lift needs testing, so start early. The same applies to telecare and door entry autodiallers.