ISDN Switch Off 2027 – Complete Guide to ISDN Line Closure & Digital Migration
The ISDN switch off is confirmed for January 31st, 2027, marking the permanent closure of all ISDN2 and ISDN30 digital lines across the UK. This BT ISDN switch off will impact thousands of businesses still relying on traditional digital telephone infrastructure for voice calls, data transmission, and connected systems.
The ISDN switch off date of January 2027 gives businesses crucial time to migrate to modern VoIP and SIP solutions. The VoIP Shop specializes in seamless ISDN-to-digital transitions, ensuring your business communications remain uninterrupted with expert guidance and cost-effective alternatives.
Don't let the ISDN switch off disrupt your business. Get expert migration support and future-proof digital solutions before the
January 2027 deadline.
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What is the ISDN Switch-Off?
(ISDN2 & ISDN30 Explained)
The ISDN switch off refers to the complete shutdown of Integrated Services Digital Network infrastructure on January 31st, 2027. ISDN technology, introduced in the 1980s, provided digital voice and data transmission over copper telephone lines, supporting multiple simultaneous calls and faster data speeds than traditional analogue systems.
When will ISDN lines switch off? All ISDN2 (basic rate) and ISDN30 (primary rate) services will permanently cease on the confirmed ISDN switch off date of January 31st, 2027. This affects every business using ISDN for phone systems, internet connectivity, or connected devices like payment terminals and alarm systems.

Unlike the gradual PSTN phase-out, the BT ISDN switch off represents a hard cutoff date where all digital lines stop functioning simultaneously, making early migration planning essential for business continuity.
Key Dates for the ISDN Switch Off
The ISDN switch off timeline provides crucial milestones that every business must understand to plan their migration effectively:
September 2023 - BT stopped accepting new ISDN orders, meaning no new ISDN2 or ISDN30 installations are possible. Businesses requiring additional lines must now consider digital alternatives.
January 2024 - The formal withdrawal period began, with telecommunications providers actively encouraging customers to migrate to VoIP and SIP solutions through targeted communication campaigns.
January 31st, 2027 - The final ISDN switch off date when all ISDN services permanently cease. This is a hard deadline with no further extensions planned.
2026 - The final year for comfortable migration planning. Expect longer installation queues and limited technical resources as remaining businesses rush to upgrade their systems.

Planning your migration during 2024-2025 ensures adequate time for system selection, thorough testing, staff training, and resolving any technical challenges before the final deadline approaches.
How Do You Start the Process of Switching from ISDN to VoIP with The VoIP Shop?
Beginning your ISDN to VoIP migration with The VoIP Shop ensures systematic planning and expert guidance
throughout your successful implementation:
Step 1:
Free System Assessment
Our technical team documents all your current ISDN usage including phone systems, internet connections, payment terminals, and connected devices. This comprehensive infrastructure audit prevents overlooked systems causing problems after your migration.
Step 2:
Requirements Planning
We help establish your must-have features, budget parameters, and timeline constraints. The VoIP Shop considers your future growth plans and advises whether you need advanced features like call recording, mobile apps, or CRM integration.
Step 3:
Tailored Solution Design
As VoIP specialists with proven ISDN migration experience and UK-based support, The VoIP Shop designs bespoke solutions matched to your specific business requirements and technical environment.
Step 4:
Detailed Implementation Proposal
We provide comprehensive written proposals including system specifications, implementation timelines, ongoing costs, and support arrangements. Our transparent pricing shows total cost of ownership, not just initial setup fees.
Step 5:
Professional Migration Planning
The VoIP Shop develops detailed implementation schedules including testing phases, staff training, and fallback procedures. We manage parallel system running during transition periods to minimise your business risk.
Step 6:
Expert Implementation Support
Our experienced engineers implement your migration systematically, ensuring thorough testing and comprehensive staff training before complete cutover from your ISDN systems.
Ready to begin your ISDN to VoIP migration? Start with our proven 6-step process and expert guidance every step of the way.
Why is ISDN Being Phased Out?
ISDN is being phased out because the 40-year-old technology cannot meet modern business communication demands. The ISDN switch off eliminates expensive maintenance costs for aging digital infrastructure that lacks the flexibility and features of modern IP-based systems.
Modern VoIP networks offer superior call quality, advanced collaboration features, and seamless integration with business applications that ISDN simply cannot provide. The switch also reduces operational overhead for telecommunications providers, enabling them to focus resources on faster, more reliable fiber and IP networks.
Additionally, ISDN's circuit-switched architecture is inefficient compared to packet-switched IP networks, which dynamically allocate bandwidth and support multimedia communications essential for today's digital workplace requirements.
Who Will the ISDN Switch Off Affect?
The ISDN switch off will impact every UK business currently using ISDN2 or ISDN30 lines for telecommunications, data transmission, or connected systems. Understanding your exposure to the BT ISDN switch off is crucial for planning an effective migration strategy. Here's who needs to prepare:
Small to Medium Businesses
Companies using ISDN2 lines for basic telephone systems, internet connectivity, or small call centers must migrate to VoIP alternatives. Many SMBs rely on ISDN without realizing their vulnerability to the switch-off.
Large Enterprises & Call Centers
Organizations with ISDN30 primary rate connections supporting high-volume calling, multiple locations, or complex PBX systems face the most significant migration challenges requiring careful project planning.
Retail & Hospitality
Businesses using ISDN for card payment terminals, booking systems, or point-of-sale connectivity need immediate attention to prevent transaction processing failures after the switch-off.
Healthcare & Emergency Services
Medical facilities, emergency services, and care providers using ISDN for critical communications, patient monitoring, or alarm systems must ensure continuity of life-safety services.
Industrial & Manufacturing
Companies with ISDN-connected telemetry, building management systems, or remote monitoring equipment need comprehensive audits to identify all affected systems before January 2027.
Not sure if the ISDN switch off affects your business? Get a professional assessment of your
current systems and migration needs.
What Systems Will Stop Working After ISDN Switch Off?
The ISDN switch off will disable all systems dependent on ISDN2 and ISDN30 connections, potentially causing severe business disruption if not addressed. Beyond basic telephone services, many critical business systems rely on ISDN infrastructure.
Here's what you need to audit and replace:
ISDN Telephone Systems
All digital phone systems using ISDN2 (2-channel) or ISDN30 (30-channel) connections will cease functioning. This includes desk phones, conference systems, and integrated communications platforms.
Internet & Data Connections
ISDN-based internet connections and data circuits used for backup connectivity or primary access in rural areas will stop working, requiring fiber or SoGEA alternatives.
Payment & Transaction Systems
Card machines, EPOS terminals, and payment processing equipment using ISDN for transaction authorization will fail, preventing customer payments and causing revenue loss.
Security & Safety Systems
Fire alarm monitoring, burglar alarm systems, CCTV networks, and access control systems transmitting over ISDN lines will lose connectivity, compromising business security.
Building Management Systems
Lift emergency phones, heating controls, lighting management, and environmental monitoring systems using ISDN connections will become non-functional without digital alternatives.
Remote Monitoring Equipment
Industrial telemetry, utility monitoring, vending machines, and remote site management systems will lose connectivity, affecting operational visibility and control.
Worried about which of your systems will fail after the ISDN switch off? Get a comprehensive
audit of all your vulnerable equipment.
What is Replacing ISDN? (VoIP & SIP Solutions)
The ISDN switch off requires migration to modern IP-based communication systems that offer superior functionality and cost-effectiveness. The VoIP Shop provides two primary replacement solutions tailored to different business needs:
VoIP Phone Systems
Complete cloud-based telephone systems that replace ISDN infrastructure entirely. VoIP delivers calls over your internet connection, providing unlimited scalability, advanced features, and significant cost savings compared to traditional ISDN lines.

Our VoIP Phone Systems include auto-attendant, call recording, voicemail-to-email, mobile apps, and integration with business applications. Perfect for businesses wanting modern communication features with simplified management.
Benefits of Switching from ISDN to VoIP:
- Dramatic Cost Reduction - Save up to 60% on monthly line rental and call charges compared to expensive ISDN maintenance and usage fees.
- Unlimited Scalability - Add or remove users instantly without physical line installations or costly engineer visits required for ISDN expansion.
- Advanced Business Features - Access call analytics, CRM integration, video conferencing, and collaboration tools impossible with basic ISDN technology.
- Complete Location Flexibility - Enable remote working and hot-desking with the same business number accessible from anywhere with internet connectivity.
- Superior Call Quality - Experience HD voice clarity and eliminate the line noise and connection issues common with aging ISDN infrastructure
Ready to upgrade from outdated ISDN to modern VoIP technology? Discover how our solutions
 can transform your business communications
SIP Trunking Solutions
For businesses with existing PBX systems, SIP trunking provides digital connectivity that replaces ISDN2 and ISDN30 lines while preserving your current phone system investment. SIP trunks deliver calls over your internet connection with better reliability and lower costs.

SIP Trunking Services from The VoIP Shop offer seamless integration with your existing PBX, number porting, and flexible channel allocation to match your calling patterns exactly.
Benefits of Switching from ISDN to SIP Trunking:
- Preserve Existing Investment
- Keep your current PBX system whilst eliminating expensive ISDN line rental and moving to cost-effective digital connectivity.
- Instant Channel Flexibility -
Scale calling capacity up or down immediately without waiting for physical line installations or costly ISDN upgrades.
- Geographic Independence -
Connect multiple office locations through a single SIP trunk without requiring separate ISDN30 installations at each site.
- Built-in Disaster Recovery -
Automatically reroute calls to mobile or alternative locations when your main system fails, impossible with fixed ISDN lines.
- Future-Ready Architecture - Prepare for eventual PBX replacement whilst maintaining current operations, creating a migration path to full cloud systems
Want to keep your existing PBX but replace expensive ISDN lines? SIP trunking gives you the best of both worlds.
Broadband Solutions for Post-ISDN Business Communications
Successful ISDN migration requires robust internet connectivity to support your new VoIP or SIP services. The VoIP Shop provides enterprise-grade broadband solutions designed specifically for business communications:
Dedicated Business Fiber (FTTP)
Full fiber connections deliver guaranteed bandwidth and low latency essential for high-quality VoIP communications. Our Superfast Business Broadband includes Quality of Service prioritization, ensuring crystal-clear voice calls even during peak internet usage.
SoGEA Business Connections
Single Order Generic Ethernet Access provides reliable broadband without requiring a separate phone line, making it ideal for the post-2027 digital landscape. SoGEA Business Broadband offers fast installation, predictable costs, and perfect compatibility with VoIP services.
Benefits of Migrating from ISDN Before the Switch Off
- Avoid Complete Service Disruption -
Early migration ensures your phone systems, data connections, and integrated business applications continue operating without interruption when ISDN services terminate.
- Preserve Your Business Numbers -
Migrate your existing ISDN numbers to VoIP or SIP systems well before the deadline to guarantee retention of established business contact information.
- Protect Payment Processing -
Ensure card machines and payment terminals remain functional by upgrading connectivity before the rush, preventing revenue loss during the transition period.
- Secure Connected Safety Systems -
Alarm systems, emergency communications, and monitoring equipment need compatible digital alternatives tested and operational before ISDN closure.
- Future-Proof Your Communications -
Modern VoIP systems offer advanced features like mobile integration, video conferencing, and collaboration tools that enhance productivity beyond basic telephony.
- Reduce Long-Term Operating Costs -
Digital communications typically cost less than maintaining ISDN infrastructure, especially when bundled with business broadband and additional services.
- Access Expert Implementation Support - Early planning allows time for proper system design, staff training, and ongoing support from experienced providers like The VoIP Shop.
Things to Consider Before the ISDN Switch Off
Before migrating from ISDN to digital alternatives, careful planning ensures smooth transition and optimal system
selection for your business requirements:
Audit All Connected Systems
Document every device using ISDN connections, including phones, payment terminals, alarm systems, and monitoring equipment. Many businesses discover unexpected ISDN dependencies during comprehensive audits.
Assess Current Call Patterns
Analyse your monthly ISDN bills to understand peak calling times, average concurrent calls, and destination patterns. This data helps size your new VoIP or SIP solution correctly.
Evaluate Internet Connectivity
VoIP requires reliable broadband with sufficient bandwidth and low latency. Consider upgrading to business fibre if your current connection can't support quality voice communications.
Plan for Staff Training
New systems include advanced features that require user education. Budget time and resources for training staff on modern communication tools and interfaces.
Consider Compliance Requirements
Some industries have specific requirements for call recording, data retention, or emergency communications that must be maintained during the migration process.
Budget for Integration Costs
Factor in potential costs for integrating new phone systems with existing CRM software, accounting systems, or other business applications currently connected to ISDN.
What Questions Should You Be Asking About the ISDN Switch Off?
Successful ISDN migration requires asking the right questions to ensure your chosen solution meets current needs and future growth plans:
- Which digital solution best fits our business? Consider whether cloud-based VoIP, on-premise systems, or hybrid SIP trunking approaches align with your operational requirements and technical preferences.
- How will the switch affect our existing phone numbers? Ensure your chosen provider can port all your ISDN numbers without disruption and understand any limitations or delays in the porting process.
- What happens to our current phone system investment? If you have a recent PBX installation, explore SIP trunking options that preserve your hardware investment whilst providing digital connectivity.
- Can our internet connection support VoIP? Assess whether your current broadband offers adequate bandwidth, quality of service, and redundancy for business-critical voice communications.
- What additional features become available? Understand how modern systems can improve your business operations through mobile integration, collaboration tools, and advanced call management features.
- How do we maintain service during the transition? Plan for parallel running, testing periods, and fallback procedures to ensure business continuity throughout the migration process.
- What ongoing support is available? Evaluate providers based on their UK-based support, technical expertise, and track record with ISDN migrations for businesses similar to yours.
Your ISDN Migration Action Plan
With the ISDN switch off date set for January 2027, proactive planning ensures smooth transition without business disruption. Start by conducting a comprehensive audit of all systems using ISDN2 or ISDN30 connections, including phones, payment terminals, alarms, and monitoring equipment.
Next, engage with The VoIP Shop to assess your specific requirements and design appropriate VoIP, SIP, or hybrid solutions that match your business needs and budget. Our UK-based experts provide comprehensive migration planning, implementation support, and ongoing management.
Don't wait until 2026 when installation queues lengthen and technical resources become scarce. Begin your ISDN migration today to ensure seamless transition, comprehensive testing, and staff training on new systems.
Frequently Asked Questions About ISDN Switch Off
When will ISDN lines switch off?
The ISDN switch off date is confirmed for January 31st, 2027. All ISDN2 and ISDN30 services will permanently cease on this date across the UK.
Can I keep using ISDN after 2027?
No, the BT ISDN switch off is mandatory. All ISDN services will stop working permanently on January 31st, 2027, requiring migration to VoIP or SIP alternatives.
Will I lose my business phone numbers?
No, you can port your existing ISDN numbers to new VoIP or SIP systems. You can migrate your business phone number easily with The VoIP Shop. Early migration ensures successful number retention without any last-minute complications.
What happens if I don't upgrade before the switch off?
In that case, your ISDN-dependent systems will stop working entirely, including phones, payment terminals, alarms, and data connections, potentially causing severe business disruption.
How long does ISDN to VoIP migration take?
Migration typically takes 2-4 weeks for standard installations, but complex systems may require longer. Early planning ensures adequate time for testing and staff training.
Will VoIP work during power outages?
Modern VoIP systems include battery backup options and mobile failover capabilities that can provide better resilience than traditional ISDN during outages.
Can I migrate gradually or must it be all at once?
You can implement hybrid solutions using SIP trunking to migrate gradually while maintaining existing PBX systems, or switch completely to cloud-based VoIP for maximum benefits.
