The PSTN Switch-Off: What It Means for UK Businesses

The UK’s Public Switched Telephone Network (PSTN), the traditional copper-based landline system that has powered business communications for decades is being permanently switched off. It’s a milestone in telecommunications history, signalling the end of analogue voice lines and the rise of fully digital, internet-based communications. For businesses of all sizes, the switch-off represents both a logistical challenge and a major opportunity to modernise.

Understanding the PSTN Switch-Off

The PSTN, along with its digital counterpart ISDN (Integrated Services Digital Network), has underpinned fixed-line telephony for more than 40 years. However, the infrastructure is ageing, expensive to maintain, and increasingly incompatible with the digital communications landscape. BT Openreach has therefore committed to retiring the entire network, transitioning all services to IP (Internet Protocol) technology that operates over broadband or fibre connections.

From 2023 onwards, new PSTN and ISDN lines are no longer being sold, and the full network shutdown is planned to complete by January 2027. Some businesses are already experiencing stop-sell restrictions, meaning they can’t add or move existing lines. While 2027 might seem distant, the transition is complex and acting early is vital to avoid disruption.

Why the PTSN Switch-Off Matters

The most obvious impact is on telephony. Any business still using analogue or ISDN phone lines will lose service when the switch-off occurs unless they move to an IP-based system such as VoIP or hosted telephony. But the effects reach far beyond voice calls. Many less obvious systems rely on the PSTN, including alarms, door entry systems, lift phones, payment terminals, fax machines, and even some broadband connections. Once the copper network is removed, these services will stop working unless they’re upgraded or replaced.

For many organisations, the PSTN switch-off is therefore a business continuity issue. Losing connectivity or payment capabilities could disrupt operations, compromise safety systems, and damage customer relationships. Yet, it also represents an opportunity: IP-based communication systems are more flexible, feature-rich, and cost-effective. They support remote work, integrate easily with cloud tools, and can scale with your business needs.

The Business Implications

Voice systems are the most directly affected. Traditional on-premise PBXs using ISDN will need to be replaced or migrated to digital alternatives such as SIP trunking or hosted cloud telephony. These systems route calls over the internet rather than fixed copper lines, enabling businesses to retain their phone numbers while gaining advanced features like call routing, mobile integration, and analytics.

Broadband services that rely on the PSTN such as ADSL and some FTTC connections will also become obsolete. Businesses should assess their current connectivity and plan to move to fibre-to-the-premises (FTTP) or other high-capacity IP connections. This upgrade is not only necessary for voice continuity but also essential to support modern digital applications, from video conferencing to cloud storage.

Alarm systems, door entry intercoms, and POS terminals are another key area of concern. Many older systems use dial-up connections that depend on PSTN lines. These must be reconfigured to work over IP or replaced with cellular-enabled alternatives. Failing to address these hidden dependencies could result in malfunctioning equipment or compliance issues when the network shuts down.

How Businesses Should Prepare for the PSTN Switch-Off

The first step in preparing for the PSTN switch-off is conducting a full audit. Identify every system in your organisation that connects via a traditional phone line - not just your phones, but also security systems, lifts, card machines, and even fax lines. Once you know what’s at risk, you can plan a phased transition.

Next, review your internet connection. Voice over IP is only as reliable as the network it runs on, so ensure you have sufficient bandwidth, low latency, and a backup connection in place. This may involve upgrading to fibre broadband or leased lines, both of which offer higher resilience and quality of service.

When planning your migration, it’s wise to move early. Waiting until 2026 or 2027 could mean long lead times and limited provider availability. An early migration also gives you time to test new systems, train staff, and adapt workflows. Many providers offer managed migration services that include number porting, system installation, and user onboarding, making the process smoother and more predictable.

The Opportunity Ahead

While the PSTN switch-off might sound like an administrative burden, it’s also a chance to modernise. Digital communications open the door to powerful features such as unified communications, call recording, voicemail-to-email, mobile extensions, and CRM integration. These tools improve collaboration, support hybrid working, and give businesses a more professional customer experience.

Moreover, IP-based systems are typically more cost-efficient. Businesses can reduce line rental costs, simplify maintenance, and pay only for the capacity they need. With cloud-based telephony, scaling up or down becomes seamless, making it ideal for growing or seasonal operations.

Final Thoughts

The PSTN switch-off marks the end of a telecommunications era and the beginning of a fully digital future. For businesses, the question is not if they will migrate, but when and how effectively they manage the transition. Those who plan early will not only avoid disruption but also gain a more agile, resilient, and connected organisation.

Start by auditing your systems today, speak with your telecoms provider, and map out your migration plan. By 2027, every UK business will need to operate over IP, so the sooner you embrace the change, the better positioned you’ll be for the digital decade ahead.