With the Public Switched Telephone Network (PSTN) and Integrated Services Digital Network (ISDN) set to be phased out by 2027, research from Zen Internet has highlighted a concerning lack of preparedness among UK businesses for this monumental shift. The transition to all-IP networks promises enhanced efficiency and reliability, but for many organisations, the reality of adaptation is still far from grasped.
The study paints a worrying picture: only 18% of small businesses and 26% of large businesses have implemented a post-PSTN solution. While some progress is being made, with 27% currently exploring their options and 19% actively migrating to new systems, 17% remain undecided on their next steps. Perhaps most troubling, nearly one in ten businesses are entirely unaware of the impending switch-off.
The PSTN, often referred to as the traditional landline system, is an analogue network that has been the backbone of telecommunications for decades. ISDN, an enhancement of PSTN, allows for digital transmission but relies on the same ageing infrastructure. As these networks are replaced by all-IP (digital) solutions, businesses must act swiftly to avoid disruption.
Time is of the essence. By December 2025, businesses could be given as little as 90 days’ notice to transition or risk losing access to vital communication and operational systems. This is more than a technological upgrade; it’s a lifeline for businesses reliant on reliable connectivity.
David Barber, Strategy Director at Zen Internet, underscores the urgency. “While awareness of the switch-off is relatively high, there’s a significant gap between knowledge and action. Too many businesses are leaving their transition to the last minute, which could result in severe disruption.”
Delaying the migration to all-IP networks carries substantial risks. The ageing PSTN infrastructure is already showing its limitations, with users reporting increased downtime and reliability issues. As the switch-off approaches, these problems are only set to worsen.
For businesses, failure to migrate could lead to complete loss of phone connectivity, critical phone numbers, and dependent systems such as payment processing, security, and IoT devices. A rushed migration could also result in poor choices, with businesses adopting suboptimal solutions that fail to meet their specific needs.
Barber advises businesses to act now: “Preparation is key. Start by assessing what’s available in your area, auditing systems dependent on the current network, and engaging with technology partners to explore the best solutions.”
While the transition presents challenges, it also offers opportunities. Moving to all-IP solutions not only ensures continuity but opens the door to advanced features and greater flexibility in communications. Early adopters can gain a competitive edge, leveraging enhanced technology to improve operations and customer experiences.
“Making the switch ahead of the deadline isn’t just about avoiding disruption,” Barber adds. “It’s a chance to unlock the full potential of digital communications and position your business for growth.”
The shift to all-IP is not merely a technical upgrade; it’s a fundamental change that will redefine how businesses operate. As the 2027 deadline looms, businesses must act decisively to secure their future in a digital-first world.
