PSTN Switch Off: How UK Businesses Can Secure Seamless Migration to VoIP

Meta Description: Explore the PSTN switch-off deadline (31 Jan 2027) and discover how UK businesses can migrate to VoIP without disruption. Expert guide to migration planning, VoIP solutions, and cost savings.

Quick Answer

The UK's Public Switched Telephone Network (PSTN) is being permanently switched off by 31 January 2027, with BT recommending businesses complete migration by the end of December 2025. Moving to VoIP (Voice over Internet Protocol) is the only viable alternative—replacing copper-based analogue lines with internet-based digital voice. UK businesses that act now can eliminate service disruption, reduce telephony costs by up to 80%, and gain modern features like video conferencing and unified communications that PSTN simply cannot deliver.

What is the PSTN and Why is it Being Switched Off?

The Public Switched Telephone Network is the UK's aging copper-based telephone infrastructure that has been operational since 1876. While historically reliable for voice calls, PSTN technology is fragile, expensive to maintain, and fundamentally incompatible with modern business communications—video calls, cloud applications, remote working, and real-time collaboration tools.

Openreach (BT's wholesale division) and other UK network operators are retiring PSTN because maintaining legacy copper infrastructure diverts critical resources away from full-fibre broadband rollout. The UK government's target of 85% gigabit-capable broadband coverage by 2027 requires accelerated investment in modern fibre networks, making the PSTN financially untenable.

This means: Your business cannot operate legacy PSTN lines beyond 31 January 2027. Any system reliant on analogue phone lines—office phones, fax machines, alarm systems, payment terminals, lifts, and telecare devices—will cease functioning without replacement. This is why reliable business broadband solutions are now essential infrastructure.

Key Dates You Cannot Miss

September 2023 – "Stop-Sell" nationwide

No new PSTN lines available; existing lines entering end-of-life phase.

End of December 2025 – BT business migration deadline (recommended)

Final safe window before infrastructure fragility increases; avoid last-minute rush. This is the critical window for planning your VoIP phone system implementation.

31 January 2027 – Final PSTN/ISDN shutdown

All remaining analogue services cease permanently.

Why December 2025 matters for your business: While the formal deadline is January 2027, BT explicitly recommends business migration by year-end 2025. This reflects the fragility of aging copper infrastructure and the reality that engineer availability and porting queues will be saturated as 2027 approaches. Waiting until the final deadline creates severe operational risk.

Why VoIP is the Essential Replacement

Voice over Internet Protocol replaces analogue copper lines with digital voice transmission over your broadband connection. Unlike PSTN—which only carries voice calls—VoIP integrates seamlessly with modern business tools, enabling video conferencing, instant messaging, call recording, intelligent call routing, and geographic flexibility. When paired with business-grade broadband, VoIP delivers enterprise-level communications that legacy systems cannot match.

VoIP vs. PSTN: The Business Case

Cost per line: PSTN costs £20-30/month versus VoIP at £5-12/month, delivering 60-80% savings across your estate. This cost reduction directly impacts your bottom line while enabling investment in more advanced communications features.

Call routing: PSTN is fixed to physical locations, while VoIP provides geographic independence for remote workers and multi-site coordination. This flexibility is essential for modern business voice and unified communications strategies.

Video capability: PSTN offers none, but VoIP has native integration for hybrid working and client presentations through seamless Microsoft Teams integration.

Features: PSTN provides only basic hold and transfer, whereas VoIP includes call recording, auto-attendant, and IVR for professionalism and compliance.

Scalability: PSTN requires new copper lines for expansion, but VoIP allows instant user additions via software—startup-ready and future-proof. This scalability makes VoIP the natural choice for growing businesses.

Integration: PSTN operates standalone, but VoIP integrates with Microsoft Teams, Slack, and CRM systems for unified workplace operations. Proper cloud connectivity solutions ensure seamless integration across all your business applications.

Reliability (SLA): PSTN offers best-effort service, while VoIP delivers 99.9% uptime SLAs with business continuity guarantees. This reliability is backed by enterprise-grade cybersecurity to protect your communications infrastructure.

This isn't just a replacement—it's a business upgrade. VoIP delivers capabilities that PSTN never could, transforming communications from a cost centre into a competitive tool.

The Business Impact of Inaction

Delaying migration creates cascading operational and financial risks. As Openreach prioritises fibre rollout, PSTN maintenance resources diminish. Lines increasingly fail without rapid repair—emergency response times extend from hours to days. A critical call system failure during peak trading could cost £500-1,000+ per hour in lost productivity.

Compliance Breaches: Fire alarm systems, emergency phones, and access control systems relying on PSTN will stop functioning. Buildings may fail fire safety audits; emergency response times increase; insurance policies may be invalidated. Modern unified communications systems address these compliance requirements natively.

Competitive Disadvantage: Competitors operating on modern VoIP phone systems enjoy flexibility (remote workers anywhere), efficiency (integrated tools), and cost advantage (80% savings). You're operating on infrastructure your vendor has abandoned.

Engineering Bottleneck: By late 2026, every other UK business will be migrating simultaneously. Migration queues extend; engineer availability vanishes; project costs rise due to scarcity. Early movers secure priority support and competitive pricing.

Real Cost: A mid-sized business (100 employees) delaying migration until Q4 2026 faces lost productivity during failed PSTN repairs (£5,000+), emergency engineering costs (£3,000+), compressed migration timeline adding complexity, and inability to negotiate competitive VoIP pricing. Total cost of delay: £10,000-20,000+ versus acting now.

This means: Action in Q4 2025 isn't optional—it's financial prudence.

Assessing Your PSTN Exposure: What Must Migrate

Before selecting a VoIP provider, audit every system dependent on your current PSTN lines. This assessment directly influences your VoIP selection and total migration cost. A comprehensive audit should identify all analogue dependencies and plan replacement strategies with your VoIP provider.

Primary Systems Requiring Migration

Office Telephone Systems: Traditional desk phones, key systems, or basic PBX systems; fax machines still relying on analogue lines. Modern VoIP phone systems replace these with feature-rich digital alternatives.

Security & Emergency Infrastructure: Fire alarm systems, intruder alarms with monitoring centre signalling, emergency phones in lifts/staircases, and access control intercoms. These critical systems require modern communications solutions with redundancy and failover capability.

Operational Systems: Payment terminals (card readers) with dial-up connections, lift emergency phones, telecare systems, and CCTV monitoring with telephone alerting. Upgrading these systems to modern protocols ensures continuity post-PSTN shutdown.

Connectivity Requirements: ADSL broadband delivered via PSTN copper, and ISDN lines (digital version of PSTN). Your migration to VoIP requires investment in business-grade broadband with SLA guarantees to ensure reliability.

Selecting the Right VoIP Solution for Your Business

VoIP isn't one-size-fits-all. Your business size, IT capability, and integration needs determine the optimal approach.

Hosted VoIP (Cloud-Based Telephony): Ideal for SMEs and multi-site businesses. Cost £5-12/user/month with no on-premise infrastructure required. Setup takes 2-4 weeks and delivers instant scalability with integrated features including call recording, auto-attendant, and voicemail-to-email. This approach works best when paired with reliable business broadband.

SIP Trunking (Hybrid Approach): Best for larger businesses with existing PBX systems. Cost £5-8 per trunk/month, setup takes 3-6 weeks, and allows you to retain your existing PBX investment while leveraging modern business voice connectivity.

Microsoft Teams Phone (Unified Communications): Perfect for Microsoft 365-dependent businesses seeking complete integration. Cost £4/user/month for Teams Phone license plus £1-3/month for calling plan. This unifies chat, calls, video, and files in one app, reducing tool sprawl and enabling true unified communications. Explore how Microsoft Teams Direct Routing enhances your calling infrastructure.

Critical requirement: Your new VoIP solution must support 99.9% uptime SLA with financial service credits. This guarantee is backed by enterprise-grade cybersecurity measures to protect your communications infrastructure from threats and ensure business continuity.

Planning Your Seamless PSTN-to-VoIP Migration

Migration failure risks service disruption, lost customer calls, and reputation damage. Seamless migration requires structured planning across three phases. A trusted VoIP phone system provider should guide you through each phase with expert support.

Pre-Migration Phase: 4-6 Weeks Before Cutover

• Complete PSTN audit (identify all phone lines and systems dependent on analogue connectivity)
• Identify VoIP requirements: user count, features, SLA needs, and broadband adequacy
• Request quotes from 3+ providers; compare total cost of ownership including ongoing support
• Submit Porting Authorisation Code (PAC) request to current provider
• Test integration with existing systems: Microsoft Teams, CRM, and business applications

Migration Phase: Cutover Day

Optimal approach: Staggered cutover by department (not big-bang switchover). VoIP provider routes incoming calls to new system while old PSTN line remains active (dual running) for 24-48 hours. Outgoing calls automatically route via new VoIP system. Users adjust to new phones, speed-dials, and voicemail access. Ensure your business broadband connection is stable and tested before cutover.

Post-Migration Phase: Stabilisation & Optimisation

• Validate all phone numbers are reachable; test calls from external lines
• Confirm alarm/fax systems functioning; notify monitoring centre of changes
• Collect user feedback on new VoIP phone system; identify training needs
• Monitor call quality metrics; confirm 99.9% uptime SLA is being met consistently
• Decommission old PSTN lines (avoid paying for redundant service)

Cost Analysis: VoIP ROI vs. PSTN

Businesses moving to VoIP typically recoup migration costs within 12-18 months through reduced telephony spend. For a 100-person business, annual PSTN costs are approximately £7,500 versus VoIP costs of £11,600 in Year 1 (including hardware amortization). However, when combined with business-grade broadband, the full communication solution delivers compelling ROI.

Hidden benefits—productivity gains from 1-2 hours/person/week through unified communications, reduced incident response, flexibility support, and compliance improvements enabled by cybersecurity integration—generate £6,000-8,000 value annually.

Year 2 and beyond: Service cost drops to £9,600 with £6,000 productivity gains, delivering £4,100+ net annual saving (55% reduction vs. PSTN). Payback period is 18-24 months on migration costs, with ongoing annual savings of 55%.

Action Plan: Next Steps for Your Business

Immediate (This Month): Audit your PSTN exposure using the checklist provided. Request RFQs from 3+ VoIP providers. Schedule migration workshop with provider technical team to understand your specific requirements.

Near-Term (Next 3 Months): Finalize vendor selection based on SLA guarantees and expertise. Execute PAC request to transfer phone numbers. Procure hardware and ensure business broadband capacity is adequate. Plan comprehensive testing phase.

Critical (Before December 2025): Complete cutover with your chosen VoIP phone system provider. Migrate all users and systems to VoIP. Decommission PSTN lines and confirm all systems functioning correctly.

Related AMVIA Resources

• VoIP Phone Systems for UK Businesses — Complete guide to hosted VoIP, SIP trunking, and Teams Phone options
• Business Broadband Solutions — Ensure your broadband meets VoIP bandwidth and SLA requirements with enterprise-grade reliability
• Microsoft Teams Calling & Direct Routing — Integrate VoIP with Teams Phone for unified communications across your organisation
• Unified Communications Strategy — Beyond VoIP: video, messaging, and collaboration integration for modern workplaces
• Enterprise-Grade Cybersecurity — Protect your VoIP infrastructure from fraud, breaches, and security threats
• Cloud Connectivity for Hybrid Work — Secure connectivity enabling remote VoIP access and seamless collaboration

Frequently Asked Questions

Q: Can I keep my current phone number when migrating to VoIP?

A: Yes. Your number transfers to VoIP via Porting Authorisation Code (PAC). Typically completes within 3-5 business days. Geographic numbers (020, 0121, etc.) almost always transfer; some legacy numbers may require workarounds—your VoIP provider identifies these early.

Q: What broadband speed do I need for VoIP?

A: Minimum 5 Mbps (1 Mbps per VoIP call + overhead). For 50+ users, recommend 30+ Mbps business-grade FTTP. VoIP requires stable, low-latency connection (not consumer-grade "up to" speeds). Business-grade FTTP SLA guarantees are essential for VoIP reliability.

Q: What happens if my broadband fails?

A: Calls drop. This is why dual-connectivity (secondary 4G/5G link) is critical. Automatic failover ensures calls route via backup link within seconds. Without failover, single broadband failure equals total communications outage. Dual-connectivity cost (£30-50/month) is cheap insurance versus £500+/hour downtime. Discuss redundancy options with your broadband provider.

Q: How long does migration typically take?

A: Planning to cutover: 6-8 weeks. Actual cutover: 1-2 days for small businesses; phased approach over 2-4 weeks for larger deployments. Total project timeline: 2-3 months is realistic with experienced VoIP implementation partners.

Q: Can I migrate my fax machine to VoIP?

A: Yes, but requires digital fax service (not analog fax). Options include cloud-based fax service that emails incoming faxes, or dedicated fax-to-IP gateway hardware. Most businesses move to email-based faxing (lower cost, better integration) as part of their unified communications migration.

Conclusion: PSTN Migration is Your Competitive Advantage

The PSTN switch-off isn't a disruptive deadline—it's your opportunity to upgrade communications infrastructure, reduce costs 55%, and enable modern working practices through unified communications. Businesses acting now (Q4 2025) secure competitive pricing, priority engineering, stable infrastructure, and modern capabilities. Businesses delaying until 2026-2027 face premium pricing, extended timelines, aging infrastructure risks, and forced compromises.

Your business communications are too critical to be left to chance. Act now.

Ready to migrate? Speak directly to AMVIA's VoIP and connectivity team. Call 0333 733 8050 or submit your enquiry to discuss your PSTN audit findings. We'll provide transparent pricing, guaranteed zero-downtime migration, and dedicated expert support throughout your transition to modern, reliable communications infrastructure.

Last Updated: November 2025 | Content Version: 1.0

Primary Keywords: PSTN switch-off, VoIP migration, UK businesses, December 2025 deadline, seamless migration

Target Audience: IT Directors, IT Managers, Business Owners, Operations Directors

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