The Upcoming PSTN Switch-Off: What Your Business Needs to Do

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The UK is progressing towards a fully digital phone network. While businesses are strongly encouraged to migrate off analogue services by the end of 2025, the final withdrawal of the legacy PSTN is scheduled for early 2027. If your organisation still relies on copper-based phone lines or services that plug into them, now is the time to plan your move.

This guide explains what the transition means, how it affects your systems, and the steps to take so your phones, broadband and connected devices continue to work without interruption. Carden Telecoms can help you migrate to modern, reliable alternatives with minimal disruption.

What Is the PSTN Switch-Off?

The Public Switched Telephone Network (PSTN) is the country’s long-standing, copper-based telephone system. It also underpins services like ISDN. The UK is retiring these analogue technologies in favour of IP-based voice and full fibre connectivity. For most businesses, that means moving to VoIP (Voice over Internet Protocol) for calls and upgrading access circuits to FTTP or SoGEA.

From Analogue to All-IP

With All-IP, calls and data travel over digital networks. The result is clearer audio, better reliability, and far greater flexibility for hybrid and remote work.

Why Is the Change Happening?

• Resilience: Ageing copper infrastructure is harder to maintain and increasingly prone to faults.
• Performance: IP and fibre deliver higher speeds, lower latency and improved call quality.
• Future-readiness: Digital networks scale more easily and integrate with modern collaboration tools.
• Efficiency: Streamlined infrastructure reduces complexity and long-term operating costs.

Key Dates and Milestones

• 2017: National programme to retire PSTN/ISDN announced.
• 2023: Stop-sell measures introduced. New analogue line orders are restricted and replacements are IP-based.
• By 31 December 2025: Businesses are strongly advised to complete migrations to digital voice and suitable broadband to safeguard continuity.
• January 2027: Final withdrawal of the legacy PSTN. Any remaining analogue-dependent services will cease.

In practical terms: treat 2025 as your operational deadline. Leaving it late risks project bottlenecks, limited engineer availability and potential service interruptions as the 2027 cutover approaches.

How This Affects Your Business

Any service that relies on an analogue line will be impacted. Typical examples include:

• Traditional desk phones and on-premise PBX systems without IP capability
• Broadband delivered over analogue pairs (ADSL/FTTC)
• Connected devices such as alarms, lift lines, door entry systems and fax machines
• Legacy card terminals or telemetry units that dial over PSTN

These services will require migration, replacement or reconfiguration to continue operating after the transition.

What Your Business Should Do Now

1. Audit your estate: List every line and device. Identify anything that plugs into a phone socket or relies on an analogue circuit.
2. Confirm migration paths: For telephony, plan a move to hosted VoIP or SIP. For access, assess FTTP or SoGEA; consider a leased line for critical operations.
3. Check dependent systems: Engage alarm, lift and EPOS vendors for IP-compatible options or adapters.
4. Port numbers early: Schedule number porting to avoid last-minute delays. Keep a fallback call routing plan for the change window.
5. Implement QoS and resiliency: Prioritise voice traffic and add backup connectivity where needed.
6. Train users and update processes: Brief staff on new devices, softphones and call flows before go-live.

Benefits of Moving to VoIP and Fibre

• Lower total cost: Simplified billing and reduced maintenance overheads.
• Flexibility: Use desk phones, mobiles or softphones with the same number.
• Advanced features: IVR, call queues, analytics, voicemail-to-email and CRM integrations.
• Scalability: Add or remove users quickly without new copper lines.
• Quality and reliability: Clearer audio and stronger SLAs on business-grade circuits.

Explore modern telephony with Carden Telecoms VoIP solutions.

Common Misconceptions

• “We can keep our analogue lines until we are ready.” Stop-sell policies limit changes and replacements. Planning ahead prevents service risk.
• “VoIP will be unreliable.” With business-grade fibre or a leased line, VoIP is highly stable and designed for enterprise use.
• “We will lose our main number.” Business numbers can be ported to your new IP platform with an agreed changeover window.
• “Migration means long downtime.” With proper staging, testing and overlap, cutovers can be completed with minimal disruption.

How Carden Telecoms Can Help

Carden Telecoms delivers end-to-end PSTN migration projects for UK businesses. We assess your current setup, design the right IP solution and manage the transition to keep you online and reachable.

• Discovery audit of lines, devices and dependencies
• Hosted VoIP, SIP trunks and Microsoft Teams integration
• FTTP, SoGEA and leased lines with business SLAs
• Number porting, QoS configuration and resilience planning
• UK-based support and proactive monitoring

Final Takeaways

• Treat December 2025 as your practical deadline to migrate and safeguard services.
• The legacy PSTN is due for final withdrawal in January 2027.
• Audit, plan and execute early to avoid congestion, delays and unexpected downtime.

Ready to plan your move? Speak to Carden Telecoms for a no-obligation migration assessment and timeline.

FAQ

When does the old phone network finally switch off?

The legacy platform is scheduled for national withdrawal in January 2027. Businesses are advised to complete migrations well before that date.

Do I need new broadband?

If you use ADSL or FTTC, move to SoGEA or FTTP to support digital voice services and modern SLAs.

Can I keep my existing numbers?

Yes. Numbers can be ported to your new VoIP or SIP platform with an agreed changeover date.

Will my alarms, lifts and EPOS still work?

Many analogue devices require IP-compatible replacements or adapters. Check with your vendors and plan upgrades ahead of the change.

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Disclaimer: This article provides general guidance on the UK’s move to All-IP services. Timelines and availability can vary by region and provider. For tailored advice, contact Carden Telecoms.