PSTN Switch-Off: What UK Businesses Need to Do Before January 2027

What Is the PSTN Switch-Off and Why Is It Happening?

As part of our business VoIP resource centre, this guide explains one of the most significant changes to UK telecommunications in a generation. The Public Switched Telephone Network (PSTN) is the analogue copper telephone infrastructure that has underpinned voice communications in the United Kingdom for over a century. The UK PSTN switch-off is scheduled for completion by January 2027 (Openreach/BT), at which point every analogue phone line and ISDN connection in the country will permanently cease to function. The network is being replaced with an all-IP digital infrastructure that carries voice calls as data over broadband connections rather than dedicated copper circuits.

The decision to retire the PSTN is driven by practical necessity. The copper network is ageing, increasingly expensive to maintain, and fundamentally limited in capability compared to modern IP-based alternatives. Openreach has stated that maintaining two parallel networks — copper and fibre — is neither economically viable nor technically sensible. The switch-off enables investment to be concentrated on the full-fibre and IP infrastructure that will serve the UK for the coming decades. Over 2 million UK businesses still rely on PSTN/ISDN lines (Ofcom estimates), and every one of them must complete their migration before the deadline.

The PSTN Switch-Off Timeline

Understanding the timeline is essential for planning your migration. The switch-off is not a single event on one date — it is a phased programme that has already been underway for several years.

• December 2020: Openreach announced its plan to retire the PSTN by 2025, later revised to January 2027. The company confirmed that no extensions would be granted.
• September 2023: Openreach paused new orders in over 100 exchange areas as part of the stop-sell programme. Businesses in those areas can no longer order new analogue or ISDN lines.
• 2024–2025: The stop-sell programme expanded to cover the majority of UK exchanges. Existing lines continue to work, but no new PSTN products are available in affected areas.
• 2026: Final migration period. Businesses with remaining PSTN and ISDN connections must complete their transition to IP-based alternatives. Demand for migration services is expected to peak during this period, creating potential bottlenecks in installer availability and number porting capacity.
• 31 January 2027: Hard cut-off date. All remaining analogue phone lines and ISDN connections are permanently switched off. There is no planned extension.

What the Switch-Off Means in Practice for Businesses

Any business system that relies on a traditional phone line will stop working after the switch-off date. The most obvious impact is on your main business phone system, but the PSTN carries far more than desk phone calls. Businesses must audit and migrate every service connected to their analogue or ISDN lines.

Systems commonly overlooked during migration planning include:

• Fax machines connected via a phone line — still used in legal, medical, and property sectors
• PDQ card payment terminals that dial out over a landline connection to process transactions
• Fire alarms and intruder alarm systems with dedicated PSTN lines for monitoring centre communication
• Lift emergency telephones — required by law under the Lifts Regulations 2016 to provide a two-way emergency call function
• Door entry systems that use phone line integration to call residents or staff
• CCTV monitoring systems using a phone line for remote access or alert notification
• Building management systems that report status or faults via PSTN connections

Failing to address alarm and safety systems before the deadline can create serious regulatory and safety issues. Lift emergency phones, for example, are a legal requirement — a non-functioning lift phone is a compliance breach that could result in enforcement action.

How the Switch-Off Affects Your Broadband

Many UK businesses use FTTC (Fibre to the Cabinet) broadband, which delivers fibre connectivity to a street cabinet but relies on the copper PSTN network for the final section from the cabinet to your premises. This means the PSTN switch-off could potentially affect your broadband connection as well as your phone lines.

Openreach is migrating FTTC broadband services to an all-IP delivery model (known as Single Order Generic Ethernet Access, or SOGEA) that removes the dependency on a traditional phone line. In most cases, your broadband will continue — but if you are on an older FTTC product, it is essential to check with your provider that your service will be migrated rather than simply terminated. For businesses where connectivity reliability is critical, upgrading to FTTP (Fibre to the Premises) or a dedicated leased line eliminates this risk entirely and provides the stable, symmetric bandwidth that VoIP calls require.

Your VoIP Migration Options

The most common migration path for UK businesses is to replace their ISDN-connected PBX with a cloud-hosted VoIP or UCaaS (Unified Communications as a Service) system. There are two principal approaches, and the right choice depends on your existing infrastructure.

SIP trunking replaces your ISDN lines with virtual IP-based connections whilst keeping your existing on-premise PBX hardware in place. This is the right route if your PBX is relatively modern, SIP-compatible, and has several years of useful life remaining. The external connection changes from ISDN to SIP, but your internal phone system continues to operate as before.

Hosted VoIP or UCaaS replaces the entire phone system — PBX hardware and ISDN lines — with a cloud platform. There is no on-premise equipment to manage. Staff access the system via IP desk phones, desktop softphone applications, or mobile apps. Microsoft Teams Phone is the most widely adopted hosted VoIP solution for organisations already using Microsoft 365, with Microsoft Teams now having over 320 million monthly active users globally (Microsoft 2024).

The benefits of migration extend well beyond simply meeting the deadline. Modern VoIP systems include features that ISDN cannot provide: web-based call management, mobile apps for remote and hybrid workers, Microsoft 365 integration, call recording, auto-attendant, and detailed call analytics. Most UK businesses see a 30–50% reduction in monthly telecoms costs after migration — eliminating ISDN line rental charges is typically the single largest saving.

What Businesses Need to Do Now

With the January 2027 deadline approaching, the practical steps every business should take are clear.

• Conduct a comprehensive line audit: Identify every PSTN and ISDN line your business uses, including those connected to alarms, lifts, payment terminals, and fax machines — not just desk phones. Many businesses discover lines they did not know they had during this process.
• Assess your internet connection: VoIP calls travel over your broadband or leased line. Have your connectivity tested for bandwidth, latency, jitter, and packet loss under real-world conditions to ensure it will support voice traffic reliably.
• Choose your migration path: Decide between SIP trunking (keep your PBX) and hosted VoIP or UCaaS (replace everything with a cloud platform). A managed provider can assess both options objectively based on your specific situation.
• Plan number porting early: Your existing phone numbers can almost always be retained, but porting takes 7–14 working days. As migration demand increases through 2026, porting queues may lengthen — plan early to secure your preferred migration date.
• Address non-telephony PSTN services separately: Alarm systems typically need to be upgraded to IP or 4G communicators. Lift phones require IP-compatible replacements. Payment terminals may need to switch to broadband or mobile connectivity. Each of these has its own lead time and should be addressed in parallel with your phone system migration.
• Ensure regulatory compliance: Your new VoIP system must provide access to 999 emergency services with accurate location information, as required by Ofcom regulations. This is particularly important for multi-site organisations and businesses with remote workers.

Common Concerns About the Switch-Off

Many UK business owners have understandable concerns about the PSTN switch-off. The most frequent questions relate to reliability, call quality, and cost.

On reliability: modern hosted VoIP platforms operate from geographically redundant data centres with 99.99% uptime guarantees. Call divert to mobile numbers provides an automatic safety net if your office internet connection fails. For businesses requiring the highest level of resilience, pairing VoIP with a dedicated leased line and 4G failover provides continuity that actually exceeds what a traditional PSTN line could offer.

On call quality: VoIP call quality on a properly configured connection is equal to or better than ISDN. Modern codecs deliver high-definition audio that ISDN's narrowband limitations cannot match. Quality issues — echo, delay, or dropped audio — are almost always attributable to insufficient bandwidth, high jitter, or missing QoS configuration on the network, not to VoIP technology itself.

On cost: the financial case for migration is strong. ISDN line rental alone costs £25–£50 per channel per month. A 30-channel ISDN30 circuit can cost over £1,000 per month in line rental before any call charges are added. VoIP alternatives typically deliver the same capacity for 30–50% less, with lower per-minute call rates and no PBX maintenance contracts to fund.

How AMVIA Can Help

AMVIA manages PSTN switch-off migrations for UK businesses end to end — from auditing your current lines and systems, to recommending the right VoIP solution, porting your existing numbers, configuring the new system, and providing ongoing support. AMVIA also handles the connectivity side, ensuring your broadband or leased line is ready to support VoIP calls before ISDN is removed. Whether you need SIP trunking, hosted UCaaS, or Microsoft Teams Phone, AMVIA will assess your requirements honestly and manage the entire transition. Call 0333 733 8050 to start your migration assessment today.