The PSTN switch-over: how BT is supporting businesses in the final phase

The UK is now in the final phase of one of the most significant infrastructure upgrades in a generation. The country’s copper-based Public Switched Telephone Network (PSTN) is set to be retired in less than 12 months, at the end of January 2027.

This is an essential step. The PSTN was designed for a different era and has become increasingly difficult to maintain. It can no longer support the connectivity, resilience or functionality that modern organisations – and critical national infrastructure (CNI) providers in particular – rely on today.

Delivering the network investment needed for the All-IP transition

Over many years, BT has invested billions of pounds in UK digital infrastructure, including nationwide full-fibre networks, to enable the move away from analogue technology and support next-generation connectivity and services.

These full-fibre, fully digital networks are built for speed, resilience and flexibility. They enable capabilities that legacy analogue systems simply cannot support and provide the robustness required by CNI sectors and essential public services. Crucially, this investment means the UK now has the digital foundations in place to complete the transition away from the PSTN safely and securely. It is also what allows BT to take a more proactive role as the switch-over approaches.

Stepping up our proactive support through protective migrations

As we move into the final stretch, our focus is on completing the transition for business customers who are still using PSTN-based services.

BT Business has already migrated the majority of business customers away from legacy platforms. As of January 2026, around 80% of our voice customers have moved to All-IP services. This represents significant progress, but thousands of organisations still rely on Wholesale Line Rental (WLR) and other PSTN-based services.

Where it is possible to do so, we are now carrying out protective migrations. This means proactively upgrading many remaining organisations and automatically moving their analogue services onto a digital solution. This helps ensure continuity of key services as the switch-over date approaches. In many cases, these upgrades can be completed with minimal disruption, and customers who can go through this process are now being notified.

Why customer engagement is important

However, protective migration is not suitable for every service or every organisation. That is why customer engagement remains essential.

Some services cannot be upgraded automatically and in other cases customers need to be involved to agree timings, test new solutions or confirm how services are used within their organisation.

Engagement remains vital for ensuring continuity of services and will make the process smoother and safer. It gives our business customers greater visibility of what is changing, more control over how the transition is completed, and time to address any complexities specific to their business.

Protecting critical national infrastructure

As a CNI provider ourselves, we understand how vital resilient connectivity is to the delivery of essential services across the UK.

We fully recognise the importance of upgrading critical services, and strong progress has already been made across sectors such as local and central government, emergency services and utilities. Overall volumes of CNI WLR services have reduced significantly, with the water sector and government bodies seeing reductions of around 50% over the past year.

Our priority is to ensure that CNI services are protected during the PSTN switch-over. That’s why as well as offering protective migrations and dedicated support teams, we also plan to provide a limited voice service for lines still in place for CNI customers after January 2027.

However, this will have very basic functionality that enables voice calls only, and isn’t a long-term solution, which underlines the importance of continued engagement across CNI organisations.

Completing the transition

To remain secure, resilient and future-ready, we’re urging all organisations to make the move to digital, IP-based networks by January 2027. We’re in the final stretch of a transition that is essential to maintaining continuity of service and to supporting the UK’s long-term connectivity.

We’re stepping in with protective migrations where we can, but we need customers to engage with us to ensure continuity of their services. Acting early reduces risk, avoids last-minute disruption and ensures the transition can be completed safely and on time. In all cases, we’ll explain what will change, outline available options and support customers in moving to replacement technologies ahead of the deadline.

If you have not upgraded yet, or you are unsure which services your organisation relies on, now is the time to check. You can contact BT on 0800 023 2698 for dedicated support, or visit https://business.bt.com/insights/what-is-ip-technology for more information.