The PSTN switch-off will be one of the biggest shifts in UK telecommunications for a generation. Moving from traditional copper landlines to digital, internet-based communication, completely transforms the way every organisation communicates. The decision was made by BT Openreach, the phase-out began in 2020, and the official switch-off is now scheduled for completion by 31 January 2027!
Despite years of effort to keep the PSTN and ISDN as modern as possible, the ever-changing communications landscape, increasingly diverse, flexible and digital, left these legacy networks outdated and unreliable. In short, the upkeep of these networks outweighs their usefulness and can no longer compete with newer technologies. For IT managers and decision-makers, understanding the switch-off is vital: it’s not just a compliance deadline, but an opportunity to modernise infrastructure, improve security and cut long-term costs.
What is PSTN & ISDN?
Public Switched Telephone Network (PSTN)
The Public Switched Telephone Network (PSTN) is the traditional circuit-switched telephone network that has carried voice calls in the UK for well over a century. It currently works through a dedicated copper-wire circuit between two places for the duration of a call, using analogue signalling at the local loop and digital switching at the exchange level.
Integrated Services Digital Network (ISDN)
is the upgrade with the same underlying infrastructure, providing a slightly enhanced digital call quality, but still reliant on the same physical copper plant.
Almost every traditional landline, fax machine, DECT phone system, ISDN30 PBX (private branch exchange), and a significant number of broadband connections have historically relied on PSTN infrastructure. So too have many alarm systems, payment terminals, lift emergency phones, and telecare devices been connected to this enormous network that is deeply embedded and, crucially, ageing. It’s not only the effectiveness that’s holding the legacy network back, but it’s also the cost of maintenance, which is one of the primary drivers behind the decision to decommission it entirely. You can read the foundational regulatory thinking behind this decision in Ofcom’s policy statement on the future of fixed telephone services and VoIP transition, published in 2019.
What is the PSTN Switch Off?
In 2015, BT Openreach made the big decision to bring the PSTN and ISDN to an end. A long-term plan was put in place, the phase-out began in 2020, and the roll-out is now in its final phase. The PSTN Switch Off is the official decommissioning of the Plain Old Telephone System.
Traditional PSTN lines often offer little flexibility and tie businesses to physical locations. Nowadays, with businesses expanding globally and more modern ways of working being introduced (like working from home), being tied to a physical location can hinder operations. The switch-off does, however, pose some major considerations for the way many people communicate. Any device connected to the PSTN line will be out of service after the switch-off unless it’s reconnected to an IP-based alternative; this includes phone systems, fax machines, door entry units and many more.
PSTN UK switch-off timeline
The timeline for the PSTN switch-off has been set and communicated well in advance, giving businesses plenty of runway to migrate. Here are the dates that matter most.
| Date | Milestone | What it means for your business |
| September 2023 | Openreach stop sell | No new PSTN or ISDN connections can be ordered. Existing lines continue until withdrawal. |
| Ongoing to January 2027 | Managed migration period | Providers are actively migrating customers to digital alternatives. Some exchange areas are being migrated earlier. |
| January 2027 | Full PSTN withdrawal | All remaining PSTN and ISDN lines cease to function. Any business still on the old network loses service entirely. |
The January deadline is set in stone, with Ofcom guidance on the PSTN switch-off confirming the dates and obligations throughout the migration period. It’s important to note that there are some areas that will be switched off before this date. The reason for this is that Openreach works through its exchange upgrade programme, so the effective deadline for your specific site could be earlier than January 2027.
The original deadline was set for December 2025; however, this was extended so that providers had more time to migrate customers, specifically vulnerable users who rely on telecare devices, safely to digital alternatives. Some countries like Germany, Sweden and Japan are already ahead, with their PSTN networks being fully decommissioned. We know now that early preparation is key to a seamless transition.
Why are Openreach switching the PSTN off?
The decision plan for the PSTN switch-off wasn’t made at random. This network was made during an era before the modern technology we have now. Technology like broadband, mobile and way before the existence of the internet. The infrastructure of PSTN is really expensive, and the expertise required to maintain it is becoming increasingly scarce. BT Openreach, which owns and operates the majority of the UK’s local loop, has been investing heavily in full-fibre broadband (FTTP) and needs to rationalise its infrastructure footprint to make that investment viable.
Price isn’t the only factor; PSTN’s capabilities in comparison to Voice over Internet Protocol (VoIP) are more limited. VoIP is more cost-effective, more flexible, easier to scale and supports modern features like call routing, video, unified communications, and remote working, which PSTN cannot support. According to a UK Parliament research briefing on the digital landline switchover, the number of PSTN customers fell from 5.2 million to 3.2 million between July 2024 and July 2025 alone.
There is also a capability argument. VoIP (Voice over Internet Protocol) is simply superior to circuit-switched telephony in almost every respect: it is cheaper to run, more flexible, easier to scale, and supports features such as call routing, video, unified communications, and remote working that PSTN cannot. UK Parliament research notes that the number of PSTN customers fell from 5.2 million to 3.2 million between July 2024 and July 2025, showing how rapidly the market has already moved. The switch-off is simply modernising and formalising what the market has already decided.
What devices and systems will stop working after the switch off?
Do you want to ensure that your communication services remain uninterrupted? You must upgrade your current set-up to a digital alternative before the switch-off. When switching, it’s really important to check devices you think might be connected and some devices you didn’t realise were connected. If you have any doubts, it’s always best to check with your supplier or provider. Affected equipment includes:
- Telecare and lift alarm phones
- Phone lines
- CCTV
- Door entry systems
- Credit card / payment machines
- Fax machines
WLR and other services impacted by the switch off
The switch-off will also affect Wholesale Line Rental (WLR) services, which have allowed companies to rent phone lines from network providers. WLR is also being phased out alongside the traditional PSTN, on the same January 2027 timeline.
Many auxiliary and legacy services will need to be replaced; ISDN and similar systems will need to be upgraded to modern alternatives that offer greater efficiency and integration. As organisations prepare, a thorough review is the best way to guide the transition:
- Evaluate current services: list the technologies that will be affected.
- Explore alternatives: research suitable replacements for outdated systems.
- Develop a transition plan: ensure that the current devices can be replaced in time.
Who is the PSTN & ISDN affecting?
When thinking about the upcoming switch off it is important to remember that it won’t just affect voice services, but also broadband services will require upgrading. This means that both businesses and residential customers will be affected by the switch. Most residential customers around the UK will not have to take action before the switch off as companies, such as Openreach, are currently busy rolling out the full fibre network. Businesses however, will need to research into which alternative will benefit their business best and which will prove to be the most cost effective yet modern solution for their business operations.
Residential Impact
For residential customers, the switch shall be fairly straightforward depending on whether they already have a broadband connection in place. This will be a simple switch, which will not affect any communications. If a residential customer does not however have broadband connection in place, many providers have committed to no extra charge for customers who wish to only have broadband in place to continue using landline phones. Residential customers will also be able to keep their current phone number and phone which will make the switch easier on many people.
Business Impact
The switch off will have a much greater effect on businesses due to the likeliness of their being more than just a phone line which will need to be migrated to the new digital network. Legacy services such as fax machines, telecare devices, lift phones and retail payment terminals will all require attention during the switch off. Most of the technology mentioned can be replicated and improved using digital alternatives however, some may not be which is where businesses may be required to research what options are available. The switch may also come with additional hardware cost’s if a business is currently running on legacy devices which will not be suitable for the switch off.
For public sector organisations in particular, adaptation goes beyond technology. Key considerations include:
- Infrastructure assessment: evaluate current capabilities and identify gaps.
- Technology investment: purchase modern communication solutions such as VoIP.
- Staff training: ensure teams are proficient with new systems.
- Ongoing support: collaborate with a trusted service provider.
Approached this way, the transition becomes a strategic opportunity to improve service delivery, not just a box-ticking exercise.
Are OpenReach/BT providing replacements for the PSTN switch off?
Companies such as Openreach and BT will provide alternative digital replacements for the PSTN network mainly by installing full fibre cabling across the country. Despite this being a huge benefit for residential customers, businesses will require more.
This is where Fuse 2 come in! With over 30 years of combined telecommunications knowledge and a fully independent voice and data network, Fuse 2 can offer bespoke solutions for any business. We have committed over 8 years to ensuring customers that they will have a seamless and smooth transition when migrating their current services to digital methods.
Our main aim at Fuse 2 is to not only provide world class service (including follow the sun support from highly trained technical engineers), but to work with a customer to discover which solution suits their needs best.
The opportunities and challenges of Network modernisation
The switch-off is a significant step in network modernisation. Today’s networks support technologies like VoIP and cloud-based services, improving communication efficiency, capacity and flexibility.
Even though modernisation has its striking benefits, it still has its challenges. Lots of organisations face resource constraints during the transition, and balancing day-to-day operations with new implementations can be demanding. To prepare effectively, it’s important to focus on a few key areas:
- Assess current infrastructure: evaluate existing systems and identify gaps.
- Invest in training: upskill teams on the new technology.
- Plan for scalability: ensure new systems can grow with your needs.
With strategic planning, these challenges become opportunities. Modernising your network enhances both capability and security.
Will the replacement fibre be more expensive?
The price of the switch to fibre will be different for everyone. Pricing can vary depending on what devices you may need to replace, the amount of staff and also how feature rich you would like the platform to be. However, this pricing is significantly less when compared to what the cost would be for the end user if the PSTN network continues to operate. It is also important to remember that when switching to fibre a small extra cost will get you many more benefits like faster speeds, better call quality and more advanced features.
What to do next for the PSTN Switch off
Research is key when considering your next steps for the PSTN switch off. It is important to assess your current system, what options are available in your area and also your budget. Many companies will use the switch off to their advantage by upping prices closer to the switch off date, so it is important to find a trustworthy company before the inevitable deadline.
Residential
For residential properties, the broadband provider in your area such as BT Openreach and Virgin Media will take care of all aspects of the switch off. Your provider will be in touch to discuss options in your area when it comes time for you to migrate.
Business
At Fuse 2 we can offer a bespoke service from start to finish which is fully tailored to you and your business needs. With 30 years of combined industry knowledge and experience, we have been providing businesses with state-of-the-art cloud services for many years. To find the perfect solution for you, talk to the people who have been providing VoIP long before the switch off was on the horizon!
Steps for IT managers
This switch-off will require careful, decisive planning, so a clear staged approach is needed:
Step 1 – Conduct a comprehensive infrastructure audit
Identify every device that’s reliant on PSTN and mark down the systems that need updating or replacing.
Step 2 – Set a clear timeline.
A defined schedule helps you manage resources and coordinate with suppliers for timely deployment and a smooth transition.
Step 3 – Engage in staff training.
Equip teams with the necessary skills to use new digital communication tools to minimise disruption during the shift.
Step 4 – Collaborate with suppliers and stakeholders.
Keep everyone informed of progress and challenges; open communication paves the way for a successful migration.
Cyber security considerations during the PSTN switch off
As the modernisation of networks safeguarding digital communication becomes the primary priority, the move to IP-based systems brings both stronger security features and new risks to manage. IT managers should:
- Implement robust encryption to protect data in transit.
- Update security policies so they align with the new technologies.
- Conduct regular risk assessments to identify emerging threats.
Proactive planning ensures security measures are comprehensive and adaptive, helping organisations secure their evolving infrastructure during and after the switch-off.
Protecting Vulnerable Users
One of the most important benefits of the PSTN switch-off is the impact on vulnerable customers, particularly those who rely on legacy devices like telecare alarms, hearing loops, or landlines as their sole means of contacting emergency services. This group faces genuine risk if migration is handled poorly, and as a result, has attracted the attention of Ofcom.
Ofcom has now published rules protecting vulnerable customers during PSTN migration, with strict requirements for providers. These include:
- Requirements to identify customers who may be at risk.
- To ensure continuity of emergency access throughout the migration.
- To provide better backup solutions where relevant.
For businesses and organisations that manage or support vulnerable individuals, understanding these obligations is not optional. Compliance is part of responsible migration planning, and any IP telephony partner you work with should be able to demonstrate how their solutions address these requirements.
What to replace PSTN with
Choosing the right replacement depends on the size and structure of your organisation, your existing UC (unified communications) platforms, and how much control you want over your telephony infrastructure. The main options are as follows…
SIP trunking
SIP trunking (Session Initiation Protocol trunking) is the most direct like-for-like replacement for ISDN. It delivers voice calls over your existing IP network using a Session Border Controller (SBC) to manage security and call routing. It is highly cost-effective, scales easily, and works with most existing PBX platforms. Our Fuse 2 SIP trunking solutions are built on carrier-grade infrastructure with geo-redundant Points of Presence (PoPs) to ensure the resilience and clear voice quality that your business depends on.
Hosted VoIP
Hosted VoIP moves your entire phone system to the cloud, replacing on-premise PBX hardware with a managed service. It is particularly well suited to businesses looking to reduce capital expenditure and improve flexibility for remote or hybrid workers. Features such as auto-attendant, call recording, and hunt groups are typically included as standard.
Direct Routing for Microsoft Teams
If your organisation uses Microsoft Teams as its primary collaboration platform, Direct Routing as a Service for Microsoft Teams allows you to make and receive PSTN calls directly within Teams, without the need for a separate desk phone or PBX. It connects your Teams tenant to the public telephone network via a certified SBC, giving you a single, integrated communications environment.
Hybrid migration
For larger organisations with complex legacy estates, a hybrid approach is highly recommended as it’s sometimes the most practical route. This involves migrating sites progressively, running IP telephony alongside existing ISDN circuits during a transition window, and consolidating to a fully IP environment over a defined timeline.
At Fuse 2, we work closely with our customers to design migration strategies that minimise disruption and align with their IT and business change programmes.
Common PSTN migration mistakes to avoid
Having helped a wide range of businesses migrate away from legacy telephony, we have seen the same avoidable errors come up repeatedly. Knowing what they are is the fastest way to sidestep them.
Forgetting non-voice PSTN services.
Alarms, fax lines, and payment terminals are consistently overlooked in audits and then become urgent problems close to go-live.
Underestimating broadband dependency.
If your SIP trunks will share bandwidth with general internet traffic, Quality of Service (QoS) configuration is essential for your call quality.
Choosing a provider based on price alone.
A cheap SIP trunk with poor resilience and no 24/7 support is a false economy. Your communications infrastructure is business-critical, and it needs a partner who treats it that way!
Not porting numbers in time.
Number porting takes time and requires coordination between carriers. Start the process early to avoid your existing geographic or non-geographic numbers being lost.
Ignoring the emergency services question.
All VoIP solutions must provide access to emergency services (999/112), but the location data registered with your provider must be accurate. This requires careful configuration, particularly for multi-site businesses. Otherwise, emergency responders will be sent to the wrong location; better safe than sorry!
Leaving vulnerable users to the last minute.
If your organisation supports or manages individuals who rely on telecare or personal alarms, their migration needs to be planned with extra care and completed well ahead of the deadline.
If you want to see how a well-executed migration looks in practice, read about how Fuse 2 delivered global VoIP and connectivity solutions for Infinitel, a project that required careful planning, reliable infrastructure, and the kind of responsive support that made the difference at each critical stage.
Will the replacement fibre be more expensive?
The cost of switching to fibre varies for everyone. Pricing varies depending on:
- The devices you need to replace
- The number of staff
- How feature-rich you’d like the platform to be
However, this is significantly less than the long-term cost to the end user of keeping the PSTN running. It’s also worth remembering that a small extra cost on fibre brings many more benefits, faster speeds, better call quality and more advanced features.
How Fuse 2 can support your PSTN switch off
Successfully navigating the switch-off requires more than replacing phone lines. Organisations need a clear migration strategy, the right digital technologies and ongoing support to ensure continuity.
This is where Fuse 2 comes in! With over 30 years of combined telecommunications knowledge and a fully independent voice and data network, Fuse 2 can offer bespoke solutions for any business. Our approach begins with a full assessment of your existing infrastructure, identifying the systems that rely on PSTN and recommending suitable alternatives such as VoIP and cloud-based voice solutions.
From planning and implementation through to training and ongoing support, we work alongside you to minimise disruption and future-proof your communications, keeping services reliable, secure and scalable as the UK moves towards full PSTN retirement. We’ve committed over 8 years to ensuring a seamless transition for our customers, backed by follow-the-sun support from highly trained technical engineers. You’ll be in the safest hands.
What to do next
Research is key when considering your next steps. Assess your current system, the options available in your area and your budget. Some companies will use the switch-off to their advantage by raising prices closer to the deadline, so it’s important to find a trustworthy partner well before then.
Residential
Your broadband provider, such as BT Openreach or Virgin Media, will handle the switch-off and will be in touch to discuss options when it’s time to migrate.
Business
At Fuse 2, we offer a bespoke service from start to finish, fully tailored to your needs. To find the perfect solution, talk to the people who were providing VoIP long before the switch-off was on the horizon.
Embracing the future of communication
The January 2027 deadline is closer than it looks, and the businesses that migrate early are the ones with the most options, the smoothest cutovers, and the least disruption. We work with organisations of all sizes to design and deliver PSTN migrations that are resilient, cost-effective, and built around your specific requirements, with 24/7 support and a dedicated account manager throughout. Explore Fuse 2’s SIP trunking solutions or learn more about Fuse 2’s mission and team of VoIP experts to find out how we can help you move forward with confidence.
You can also explore Fuse 2’s guides on VoIP, SIP trunking, and cloud communications for further reading on every aspect of the transition.
The Benefits of the 2027 PSTN Switch off?
In a nutshell, the PSTN switch off is going to modernise and simplify the way we all communicate by future-proofing the solutions we use. The switch off will offer many significant benefits including enhanced connectivity, greater global flexibility and improved security and reliability for both businesses and residential properties. The world is evolving with new technological advancements being created every day, so why are we relying on old communication technologies?
