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PSTN Switch-Off: How UK Businesses Can Migrate to VoIP Before 31 January 2027

The UK's Public Switched Telephone Network (PSTN) is being permanently switched off on 31 January 2027, with BT recommending businesses complete migration by December 2025. VoIP (Voice over Internet Protocol) is the only viable replacement—delivering up to 80% cost savings, unified communications, and modern features that legacy PSTN cannot provide. UK businesses that act now avoid service disruption, engineering bottlenecks, and premium pricing.

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

The PSTN is the UK's aging copper-based telephone infrastructure, operational since 1876. Openreach and other UK network operators are retiring it because maintaining legacy copper diverts resources from full-fibre broadband rollout.

This affects every system reliant on analogue phone lines:

• Office phones and fax machines
• Fire alarms and intruder alarms
• Lift emergency phones and telecare devices
• Payment terminals and access control systems

After 31 January 2027, these systems will stop working without replacement.

To ensure continuity, businesses need reliable business broadband infrastructure capable of supporting modern VoIP communications.

What Are the Critical PSTN Switch-Off Dates?

September 2023 – "Stop-Sell" Nationwide

No new PSTN lines available. Existing lines are entering end-of-life phase.

December 2025 – BT Recommended Migration Deadline

This is your critical window. BT explicitly recommends business migration by year-end 2025 due to aging copper infrastructure fragility and anticipated engineering bottlenecks.

31 January 2027 – Final PSTN/ISDN Shutdown

All remaining analogue services cease permanently.

Why December 2025 matters: By late 2026, every UK business will be migrating simultaneously. Engineer availability vanishes, porting queues extend, and project costs rise. Early movers secure priority support and competitive pricing.

Why is VoIP the Best PSTN Replacement?

VoIP replaces analogue copper lines with digital voice transmission over your broadband connection. Unlike PSTN—which only carries voice calls—VoIP integrates with modern business tools for video conferencing, instant messaging, call recording, and intelligent routing.

To explore how VoIP transforms business communications, try our VoIP Cost Savings Calculator.

PSTN Limitations:

• £20–30/month per line
• Fixed to physical locations
• No video capability
• Basic hold and transfer only
• Requires new copper lines for expansion
• Best-effort reliability (no SLA)

VoIP Advantages:

• £5–12/month per user (60–80% savings)
• Geographic independence for remote workers
• Native video conferencing integration
• Call recording, auto-attendant, IVR, voicemail-to-email
• Instant user additions via software
• 99.9% uptime SLAs with business continuity guarantees

This isn't just a replacement—it's a business upgrade. VoIP transforms communications from a cost centre into a competitive advantage.

What Happens If Your Business Doesn't Migrate?

Operational Failures

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, and insurance policies may be invalidated.

Competitive Disadvantage

Competitors on modern VoIP systems enjoy:

• Remote working flexibility
• Integrated communication tools
• 80% cost advantage

You're operating on infrastructure your vendor has abandoned.

Engineering Bottleneck (Late 2026)

Migration queues extend, engineer availability vanishes, and project costs rise due to scarcity.

Real cost of delay for a 100-person business:

• Lost productivity during failed PSTN repairs: £5,000+
• Emergency engineering costs: £3,000+
• Compressed migration timeline adding complexity
• Inability to negotiate competitive VoIP pricing

Total cost of delay: £10,000–20,000+ versus acting now.

What Systems Must Migrate from PSTN?

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.

Office Telephone Systems

• Traditional desk phones, key systems, or basic PBX systems
• Fax machines relying on analogue lines

Security & Emergency Infrastructure

• Fire alarm systems with monitoring centre signalling
• Intruder alarms
• Emergency phones in lifts and staircases
• Access control intercoms

Operational Systems

• Payment terminals with dial-up connections
• Lift emergency phones
• Telecare systems
• CCTV monitoring with telephone alerting

Connectivity

• ADSL broadband delivered via PSTN copper
• ISDN lines (digital version of PSTN)

Your migration requires business-grade broadband with SLA guarantees to ensure VoIP reliability.

Which VoIP Solution is Right for Your Business?

Hosted VoIP (Cloud-Based Telephony)

Best for: SMEs and multi-site businesses

• Cost: £5–12/user/month
• Setup: 2–4 weeks
• Benefits: No on-premise infrastructure, instant scalability, integrated features (call recording, auto-attendant, voicemail-to-email)

SIP Trunking (Hybrid Approach)

Best for: Larger businesses with existing PBX systems

• Cost: £5–8/trunk/month
• Setup: 3–6 weeks
• Benefits: Retain existing PBX investment while leveraging modern connectivity

Microsoft Teams Phone (Unified Communications)

Best for: Microsoft 365-dependent businesses

• Cost: £4/user/month for Teams Phone license + £1–3/month calling plan
• Benefits: Unifies chat, calls, video, and files in one app

For businesses already using Microsoft 365, Microsoft Teams Calling integration delivers seamless unified communications without additional platforms.

Critical requirement: Your VoIP solution must support 99.9% uptime SLA with financial service credits.

How Do You Plan a Seamless PSTN-to-VoIP Migration?

Pre-Migration Phase (4–6 Weeks Before Cutover)

1. Complete PSTN audit – Identify all phone lines and systems dependent on analogue connectivity
2. Identify VoIP requirements – User count, features, SLA needs, broadband adequacy
3. Request quotes from 3+ providers – Compare total cost of ownership including ongoing support
4. Submit Porting Authorisation Code (PAC) request – To transfer your existing phone numbers
5. Test integration – 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
• Old PSTN line remains active for 24–48 hours (dual running)
• 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)

1. Validate all phone numbers are reachable from external lines
2. Confirm alarm/fax systems functioning; notify monitoring centre
3. Collect user feedback; identify training needs
4. Monitor call quality metrics; confirm 99.9% uptime SLA
5. Decommission old PSTN lines (avoid paying for redundant service)

What is the ROI of Migrating to VoIP?

Year 1 Cost Comparison (100-Person Business)

Annual PSTN costs: ~£7,500
VoIP costs (including hardware): ~£11,600

Hidden productivity benefits: 1–2 hours/person/week through unified communications = £6,000–8,000 annual value

Year 2 and Beyond

• Service cost drops to ~£9,600/year
• Productivity gains continue at £6,000+/year
• Net annual saving: £4,100+ (55% reduction vs. PSTN)

Payback period: 18–24 months on migration costs, with ongoing annual savings of 55%.

What is Your PSTN Migration Action Plan?

Immediate (This Month)

• Audit your PSTN exposure using the checklist above
• Request RFQs from 3+ VoIP providers
• Schedule migration workshop with provider technical team

Near-Term (Next 3 Months)

• Finalize vendor selection based on SLA guarantees
• 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
• Decommission PSTN lines and confirm all systems functioning

Frequently Asked Questions

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

Yes. Your number transfers to VoIP via Porting Authorisation Code (PAC), typically completing within 3–5 business days. Geographic numbers (020, 0121, etc.) almost always transfer; some legacy numbers may require workarounds that your VoIP provider identifies early.

What broadband speed do I need for VoIP?

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 broadband with SLA guarantees is essential for VoIP reliability.

What happens if my broadband fails?

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.

How long does migration typically take?

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 implementation partners.

Can I migrate my fax machine to VoIP?

Yes, but requires digital fax service (not analog fax). Options include cloud-based fax-to-email services or dedicated fax-to-IP gateway hardware. Most businesses move to email-based faxing as part of their unified communications migration.

Transform Your Communications Before the Deadline

The PSTN switch-off isn't a disruptive deadline—it's your opportunity to upgrade communications infrastructure, reduce costs by 55%, and enable modern working practices.

Businesses acting now (Q4 2025) secure:

• Competitive pricing
• Priority engineering support
• Stable infrastructure
• Modern capabilities

Businesses delaying until 2026–2027 face:

• Premium pricing
• Extended timelines
• Aging infrastructure risks
• Forced compromises

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

Ready to migrate? Get a Free VoIP Assessment from AMVIA's VoIP and connectivity team. Call 0333 733 8050 to discuss your PSTN audit findings. We provide transparent pricing, guaranteed zero-downtime migration, and dedicated expert support throughout your transition to modern, reliable communications infrastructure.

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