Business Phone System Migration Checklist 2027: Switching to VoIP Quick Answer
UK businesses still using traditional analogue or ISDN phone services should prepare to migrate to a digital phone system ahead of the 31 January 2027 Openreach PSTN switch-off.
For many businesses, this means moving to VoIP (Voice over Internet Protocol), which carries telephone calls over an internet connection rather than the traditional telephone network.
A successful migration involves more than replacing handsets. You should check your broadband, identify equipment connected to old lines, arrange number porting, configure call routing and test the new system before disconnecting your existing service.
Our View: The biggest migration risk is not choosing the wrong VoIP handset. It’s discovering too late that a payment terminal, alarm or important business number still depends on the old telephone connection.
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Key Takeaways
The Openreach PSTN switch-off deadline is 31 January 2027 .
Businesses should check analogue lines, ISDN connections and any equipment using them.
Hosted VoIP is a common replacement for traditional SME phone systems.
Existing business telephone numbers can usually be retained through number porting.
Do not cancel your existing telephone service before the provider confirms successful number migration.
VoIP needs suitable internet connectivity and a plan for power or broadband failures.
Compare the complete cost of licences, handsets, setup, calls, porting and support.
Business Phone System Migration Checklist Use this checklist with your current telecoms provider, IT team or prospective VoIP supplier.
Step Action What to check
1
Audit existing lines
Analogue, ISDN, telephone numbers and connected devices
2
Check broadband
Capacity, reliability, Wi-Fi and wired network
3
Choose a phone system
Hosted VoIP, Teams Phone or SIP trunking
4
Check connected equipment
Alarms, lifts, intercoms, fax and card terminals
5
Plan number porting
Existing numbers, provider records and transfer date
6
Configure the new system
Users, handsets, call routing and voicemail
7
Test before switching
Incoming, outgoing, transferred and emergency calls
8
Complete migration
Confirm number transfers and retire old services safely
1. Audit Your Existing Business Telephone Lines Start by identifying what your business currently uses.
Analogue PSTN telephone lines .ISDN2 or ISDN30 services.
Existing PBX or telephone switchboards.
Direct dial numbers and main business numbers.
Fax lines and standalone telephone connections.
Broadband services associated with legacy phone lines.
Review recent telecoms bills and ask your existing provider to confirm which services are affected and when they need replacing.
Important: Not every business will follow the same migration process. Some may already use IP-based voice services without realising it.
2. Check Your Broadband and Network Readiness VoIP calls rely on suitable network connectivity, so check your existing business internet before choosing a provider, so you should review:
Available bandwidth during busy periods.
Latency, jitter and packet loss.
Router and firewall compatibility.
Wired network and Wi-Fi coverage.
Power-over-Ethernet requirements for desk phones.
Backup broadband or mobile connectivity.
A small office may be able to use its existing business broadband. Larger teams, contact centres and multi-site businesses may need more extensive network planning.
Our View: Don’t automatically buy a leased line just because you’re moving to VoIP. First assess whether your current business connection delivers the necessary call quality and resilience.
3. Choose the Right VoIP Replacement Different digital phone systems suit different business requirements.
Phone System Best Suited To Key Consideration
Hosted VoIP
Small and medium-sized businesses
Cloud-managed calling, handsets and user licences
Microsoft Teams Phone
Businesses already using Microsoft Teams
Calling plans, licensing and compatibility
SIP trunking
Businesses retaining a compatible PBX
Existing equipment and number migration
Cloud contact centre
Customer support and sales teams
Call queues, reporting and integrations
For smaller businesses replacing traditional desk phones, hosted VoIP is often a practical starting point.
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4. Check Alarms, Card Machines and Other Connected Equipment Some business devices communicate using traditional telephone lines and may stop working when those connections are withdrawn.
Equipment to check includes:
Fire and intruder alarms.
Lift emergency telephones.
Door entry and intercom systems.
Older card payment terminals.
Fax machines.
Building monitoring and other specialist devices.
Contact the equipment supplier to confirm whether the device needs replacing, upgrading or connecting through a suitable alternative service.
Our View: We would put this audit ahead of the telephone handset decision, particularly for hospitality, retail, healthcare and buildings with lift or safety equipment.
5. Plan Business Phone Number Porting Most businesses can retain eligible existing telephone numbers when switching providers through a process known as number porting.
Your new supplier will generally coordinate the transfer.
Prepare:
Current telecoms provider details.
Main business telephone number.
All additional numbers and direct dial ranges.
Account name and service address.
Relevant account references.
Preferred migration date.
Do not cancel your existing phone service before the number port is successfully completed. Cancelling prematurely can create service disruption or problems retaining numbers – also confirm whether changing or cancelling the old telephone line could affect associated broadband or other services.
6. Configure and Test the New VoIP System Set up the new phone system before transferring live customer numbers wherever possible so you should check that staff can use the equipment and that the following features work correctly:
Incoming and outgoing calls.
Business caller ID.
Call transfers and hunt groups.
Opening hours and automated greetings.
Voicemail and missed-call notifications.
Mobile and desktop calling applications.
Emergency calling and registered location information.
Call forwarding when the internet is unavailable.
Digital telephone services may stop working during a power cut unless suitable backup arrangements are in place.
Discuss emergency calling, power protection and continuity arrangements with your provider, particularly where reliable telephone access is essential.
7. Complete the Migration Without Unnecessary Downtime Choose a migration date with your provider and arrange appropriate support during the changeover so before signing off the migration:
Confirm all required numbers are working on the new system.
Test inbound and outbound calls using different networks.
Check reception and call queue routing.
Confirm voicemail and out-of-hours handling.
Check emergency calling arrangements.
Confirm associated devices have been migrated separately.
Only then arrange cancellation of redundant services, following provider advice.
For businesses where missed calls mean lost bookings or sales, arrange a fallback contact number or temporary call-routing procedure during the switchover.
How Much Does Business Phone System Migration Cost? Migration costs depend on the number of users, existing hardware, required features and contract arrangements.
Cost What to Budget For
VoIP subscription
Monthly licence fees per user or calling package
Handsets and headsets
New equipment where existing hardware cannot be reused
Setup and configuration
Call routing, accounts, training and deployment
Number porting
Any provider charges for moving telephone numbers
Network upgrades
Router, switches, Wi-Fi or connectivity improvements
Business continuity
Backup internet, power protection or call failover
Existing contract
Early termination or overlapping service charges where applicable
Illustrative example: A ten-user business quoted £15 per user per month would pay £150 monthly or £1,800 annually for those licences alone. Hardware, call charges, setup and other services may be additional. This is a calculation, not a verified supplier offer.
Our View: Request a full first-year and minimum-contract price rather than comparing headline monthly VoIP licence costs. A low-cost system may become expensive when handsets, support and essential call features are added.
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Our Verdict: How Should UK Businesses Prepare for the 2027 Switch-Off? Start by identifying the legacy telephone services and equipment your business still depends on, then choose a suitable digital replacement and plan the number transfer carefully.
Our recommendation is to prioritise three things:
Continuity: Keep customer numbers, essential devices and emergency communications working.Suitability: Choose a VoIP system that meets the business’s actual call-handling requirements.Value: Compare complete contract costs, not just the cheapest per-user subscription.
For most small businesses, the next practical step is comparing hosted VoIP providers and confirming which suppliers can manage the migration, number porting and setup.
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Business Phone Migration FAQs When is the UK PSTN switch-off? Openreach has confirmed that its PSTN network will close on 31 January 2027. Businesses still using affected analogue or ISDN services should contact their provider about migration.
Can I keep my existing business phone number? Usually, yes. Eligible business phone numbers can normally be retained through number porting. Confirm the process with your new provider before cancelling anything.
Do I need to replace all my office phones? Not necessarily. Some existing equipment may be compatible with digital calling or suitable adaptors. Check with your provider before purchasing replacements.
Does VoIP work during a power cut? Not without appropriate backup arrangements. Routers, internet equipment and many VoIP handsets need electricity, so ask about battery backup, mobile failover and emergency calling.
Can I use my existing business broadband for VoIP? Often, yes. The connection needs sufficient bandwidth, low latency and reliable performance. Your provider should assess it before migration.
How long does business phone migration take? Timescales vary with the number of users, equipment, provider setup, number porting and any network upgrades. Request a realistic implementation schedule before committing.
What happens if my business does not migrate before January 2027? Affected legacy services may stop working or move to limited temporary arrangements where eligible. Do not rely on emergency provisions to maintain normal business telephone services.
Related Business Phone Guides Compare Business Phone Systems Before the 2027 Switch-Off Whether you’re replacing a traditional office landline, migrating an ISDN phone system or moving several business locations to VoIP, comparing providers can help you choose suitable equipment, support and connectivity.
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Hi, I’m Ally Cox , a senior copywriter and blogger at CompareYourBusinessCosts.co.uk, the UK’s trusted platform for comparing business services.over a decade of experience in the B2B sector, I specialise in simplifying complex topics like leased lines, VoIP, business energy, HR and payroll solutions, accounting software, and EPOS systems .HR, copywriting, and business operations- from clocking-in systems to card machines and office technology .informed, confident decisions when choosing products and services that improve efficiency and save money.
