BT PSTN Switch-Off: What Businesses Need to Know Before January 2027

PSTN Switch-Off Article Summary

1. The deadline is 31 January 2027. BT plans to switch off its PSTN, ISDN, ADSL and other related analogue services by this date.
2. The change affects more than phone calls. Businesses need to identify alarms, lifts, payment terminals, CCTV, door-entry systems and other devices that may still rely on an analogue line.
3. Businesses should migrate now rather than wait for the deadline. Openreach and BT are actively encouraging customers that remain on traditional services to contact their providers and move to a digital solution before the switch-off.

The BT PSTN switch-off is now only months away. The UK's traditional Public Switched Telephone Network (PSTN) is scheduled to be switched off on 31 January 2027, along with ISDN, ADSL and other services that depend on the old Wholesale Line Rental (WLR) network [1].

For UK businesses that still rely on analogue phone lines, this is no longer a change to prepare for “in a few years”. The final migration is underway, and businesses must identify and move any remaining PSTN-dependent services to digital alternatives.

The change does not only affect traditional office phones. Alarm systems, lift lines, door-entry systems, payment terminals, CCTV and other equipment may also depend on analogue connections [1][2].

If your business has not completed its migration, now is the time to check exactly what still relies on the old network and prepare your move to an IP-based service such as VoIP.

What is the BT PSTN switch-off?

The Public Switched Telephone Network, or PSTN, is the traditional telephone network that has supported UK landline services for decades.

ISDN, or Integrated Services Digital Network, was introduced later and enabled digital voice and data services to operate over this traditional infrastructure.

But these legacy networks are reaching the end of their operational life. BT says the old networks are increasingly fragile, difficult to maintain and no longer capable of meeting modern communications requirements [1].

The UK's communications infrastructure is therefore moving towards digital services based on Internet Protocol (IP).

This includes technologies such as Voice over Internet Protocol (VoIP), Digital Voice and All-IP telephony [2].

Instead of carrying a voice call through the traditional PSTN, these technologies transmit communications using an internet connection.

For businesses, this transition creates an opportunity to move away from legacy phone infrastructure and towards cloud-based communication systems that can support calls across computers, smartphones and other connected devices.

When is the PSTN switch-off happening?

The key date for businesses is now 31 January 2027.

BT Business states that by this date the following analogue networks will be switched off:

• Public Switched Telephone Network (PSTN)
• Integrated Services Digital Network (ISDN)
• Asymmetric Digital Subscriber Line (ADSL)
• Other related analogue services

Together, these services form part of the Wholesale Line Rental network [1].

The original target for the PSTN switch-off was December 2025. However, the timetable was extended, with the industry taking additional measures to protect vulnerable customers and people who rely on telecare and other critical services during the migration.

Government guidance now states that PSTN-dependent devices and UK landlines need to be fully upgraded by January 2027 [2].

Openreach has also already stopped the nationwide sale of new analogue services. Customers taking out new contracts or changing eligible services are instead moved towards digital alternatives [3].

In other words, the transition is no longer approaching: it is already happening, and the final shutdown is imminent.

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What happens if you haven't switched from PSTN by January 2027?

Businesses should not assume their existing analogue services will simply continue operating after the deadline.

BT warns that services dependent on its old networks could stop working from 31 January 2027 if they have not been moved to an IP-based alternative [1].

Some customers may be automatically moved through BT's Protective Migrations programme. Where this is not possible, affected services could stop working or be transferred to a limited voice-only service [1].

Openreach similarly explains that some customers who have not migrated may be placed on Emergency Voice Access (EVAc). This is intended as a temporary measure and provides only limited voice functionality. Features such as call forwarding, caller display or voicemail may not be available [4].

Businesses should therefore not treat EVAc or protective migration as an alternative to preparing for the switch-off.

The safest approach is to identify your dependencies and complete the migration before the deadline.

How will the PSTN switch-off affect businesses?

For many businesses, the most visible change will be how calls are delivered.

Instead of using a traditional analogue or ISDN line, voice calls will operate over an IP connection.

If your company already uses a cloud phone system or VoIP solution, much of this transition may already have taken place.

The main risk lies with businesses that still use legacy lines or have equipment connected to them.

It's not just your office phones

One of the most important parts of preparing for the switch-off is identifying devices that may use PSTN without necessarily looking like telephone equipment.

Depending on your premises and infrastructure, this could include:

• analogue desk phones;
• fax machines;
• lift emergency phones;
• alarm systems;
• CCTV systems;
• door-entry systems;
• payment terminals;
• telecare or health-monitoring equipment;
• intercoms;
• other devices connected to an analogue telephone line.

Government guidance specifically warns that equipment such as alarm systems, telecare devices and door-entry systems may require upgrading as part of the transition [2].

BT also highlights equipment such as alarms, lifts and CCTV among the services businesses should check [1].

This is why a PSTN migration should begin with an audit of every analogue line in the organisation, not simply the main business telephone number.

Why is the UK switching off PSTN and ISDN?

The traditional telephone network is decades old.

According to BT, legacy networks are increasingly fragile, difficult to maintain and unable to keep pace with modern communications requirements [1].

The government similarly notes that the PSTN is ageing and that some of the equipment needed to maintain it is no longer manufactured, making replacement parts increasingly difficult to source [5].

The transition to digital communications is therefore not simply about introducing new functionality. It is also about replacing infrastructure that is becoming progressively harder to maintain.

IP-based communications can provide a more flexible foundation for modern businesses, particularly as employees increasingly communicate across offices, remote locations, computers and mobile devices.

Moving from PSTN and ISDN to VoIP

For businesses still using traditional telephony, the switch-off makes migration to an IP-based solution increasingly urgent.

VoIP transmits calls using an internet connection rather than the traditional PSTN infrastructure.

Moving to a cloud-based VoIP phone system can also provide capabilities that go beyond simply replacing an analogue phone line.

No traditional PBX hardware to manage

With a cloud phone system, employees can make and receive calls using applications on their computers and smartphones.

This reduces dependence on traditional on-premise telephone infrastructure and makes it easier to add users or adapt the phone system as the company changes.

Work from different locations

IP-based business telephony is not tied to a traditional telephone line at a particular desk.

Employees can access their business communications from the office, from home or while travelling, depending on the service and configuration used.

This can be particularly useful for organisations with hybrid, remote or geographically distributed teams.

Scale your phone system more easily

Cloud-based phone systems are delivered as software services, making it easier to add users, numbers and features as business requirements evolve.

Updates can also be deployed through the software rather than requiring companies to replace traditional telephone infrastructure each time their requirements change.

PSTN switch-off checklist: what should businesses do now?

With the January 2027 deadline approaching, businesses that have not yet completed their migration should prioritise the following steps.

1. Audit every PSTN and ISDN line

Identify all traditional telephone lines across your offices, sites and facilities.

Do not limit the audit to lines used for voice calls.

2. Identify devices connected to those lines

Check whether alarms, lifts, door-entry systems, payment terminals, CCTV, fax machines or other specialist equipment rely on PSTN connectivity.

If you are unsure, contact the equipment manufacturer, service provider or installer.

3. Check your internet connectivity

An IP-based phone system relies on your network connection.

Review your available bandwidth, network configuration and Quality of Service requirements before migrating business-critical calling.

4. Speak to your providers

If you still use analogue services, contact your communications provider and the providers of any specialist equipment connected to those lines.

Confirm whether the equipment is compatible with digital connectivity or needs to be replaced or reconfigured.

5. Plan number porting

Your established business phone numbers are valuable assets.

If you are changing provider, confirm which numbers need to be ported and build the porting process into your migration plan.

6. Test critical equipment

Do not assume a device will work correctly simply because it can physically connect to new equipment.

Test business-critical services after migration, particularly alarms, lift phones, entry systems and other safety-related equipment.

7. Don't wait until January 2027

The closer businesses get to the deadline, the less time they have to identify compatibility issues, test new equipment and resolve problems without disrupting operations.

Openreach is explicitly advising customers that remain on traditional lines to contact their providers and switch now rather than wait for 31 January 2027 [4].

What about vulnerable users and telecare devices?

The digital switchover has required particular care for people who depend on their landlines for telecare and other safety-critical services.

In 2026, communications providers and network operators remain subject to additional commitments designed to protect vulnerable customers during the migration.

The government's PSTN Charter states that known telecare users should not be migrated without confirmation that a compatible and functioning telecare solution is in place. It also addresses battery backup for customers who may need continued access to emergency services during a power cut [6].

This issue is particularly important because traditional PSTN phones and digital services do not necessarily behave in the same way during a power failure.

Businesses and organisations responsible for telecare, health, accessibility or other safety-critical services should therefore discuss their requirements directly with their communications and equipment providers rather than treating these systems as part of a routine phone migration.

Don't treat the PSTN switch-off as just a technical deadline

For years, businesses could look at the PSTN switch-off as something that would happen in the future.

That is no longer the case.

The final deadline is 31 January 2027, and the nationwide stop-sell of new analogue services has already taken place [1][3].

Businesses still relying on PSTN or ISDN should use the remaining months to identify every affected line, check connected equipment, plan their digital migration and test their replacement services.

Moving to VoIP can also be an opportunity to rethink how your teams communicate rather than simply replacing an old phone line with a digital equivalent.

A cloud phone system can give employees greater flexibility, simplify the management of business numbers and make communications accessible across different locations and devices.

Ready to switch from PSTN to VoIP?

If your business still relies on PSTN or ISDN, the January 2027 deadline is now close enough that migration should be treated as a priority.

Start by auditing your existing phone lines and connected equipment, then plan your move to an IP-based business phone system before legacy services are withdrawn.

Contact our experts to discuss your migration to Ringover and schedule your free demo.

FAQ: BT PSTN and ISDN switch-off

When will BT switch off the PSTN?

BT plans to switch off its traditional PSTN network by 31 January 2027 [1]. Businesses still using PSTN-dependent services should migrate to a digital alternative before this deadline.

Has the PSTN switch-off been delayed?

Yes. The original target was December 2025, but the timetable was extended. The current deadline for BT's PSTN switch-off is 31 January 2027 [1].

Is ISDN being switched off too?

Yes. BT states that PSTN, ISDN, ADSL and other related analogue services forming part of the WLR network will be switched off by 31 January 2027 [1].

What will replace PSTN in the UK?

Traditional analogue landlines are being replaced by digital services using technologies such as VoIP, Digital Voice and All-IP telephony [2].

What happens if my business doesn't switch before January 2027?

Services that still rely on the old network could stop working, be moved through a protective migration process or, in some circumstances, be placed temporarily on a limited emergency voice-only service [1][4]. Businesses should migrate before the deadline rather than rely on these fallback measures.

Can I keep my business phone number when moving to digital telephony?

Existing numbers can generally be retained when moving to digital phone services. If you are changing provider, check your number-porting requirements in advance and include them in your migration plan.

Will alarms and lift phones be affected by the PSTN switch-off?

Potentially. Alarms, lift lines, CCTV, door-entry systems, telecare devices and other equipment can rely on analogue telephone connections [1][2]. Businesses should identify these devices and check their compatibility with their equipment or service provider before migration.

Citations

• [1]https://business.bt.com/help/article/phone-line-and-services/move-from-traditional-lines-to-the-cloud/the-pstn-and-isdn-switch-off-what-it-means-for-you/
• [2]https://www.gov.uk/guidance/moving-landlines-to-digital-technologies
• [3]https://www.openreach.com/news-and-opinion/2023/openreach-change-telephone-network
• [4]https://www.openreach.com/big-switch-off/digital-phonelines-for-homes
• [5]https://www.gov.uk/government/publications/telecare-national-action-plan-protecting-telecare-users-throughout-the-digital-phone-switchover/telecare-national-action-plan-protecting-telecare-users-through-the-digital-phone-switchover
• [6]https://www.gov.uk/government/publications/public-switched-telephone-network-charter/public-switched-telephone-network-charter

Published on October 7, 2026.