PSTN and ISDN Switch-Off: A 2027 Checklist for UK Businesses
The UK’s traditional Public Switched Telephone Network (PSTN) and ISDN services are being replaced by digital connectivity. Current government guidance states that users of the Openreach PSTN should be migrated to new services by 31 January 2027.
For businesses, this is not only a telephone-system project. Analogue lines can support alarms, lift emergency phones, card terminals, entry systems and other equipment that may be overlooked during a straightforward phone upgrade.
What is changing?
Traditional copper-based voice services are being retired and calls are moving to internet-based technology such as hosted Voice over Internet Protocol (VoIP). A digital phone system can provide useful features and greater flexibility, but it relies on suitable connectivity and power.
Businesses should therefore identify every service that uses an analogue line and plan an appropriate replacement before the final migration date.
1. Audit every telephone line
Create a record of all business numbers and lines, including their location, purpose, supplier and monthly cost. Do not assume that an apparently unused line has no function.
- Main and secondary telephone numbers
- Fax lines
- Broadband and backup connections
- Alarm and CCTV connections
- Lift and emergency telephones
- Door-entry and intercom systems
- Card machines and tills
- Franking, vending and telemetry equipment
- Building-management and monitoring systems
2. Speak to specialist equipment providers
Some equipment cannot simply be plugged into a digital phone adapter. Contact the company responsible for each alarm, lift, payment or monitoring system and confirm which replacement connection it supports.
Record who is responsible for upgrading each item and whether engineering work, replacement hardware or a new mobile or internet connection is required.
3. Check broadband capacity and resilience
Hosted VoIP depends on a stable internet connection. Review the number of users, expected call volume, other network traffic and whether the current broadband service provides enough capacity.
Consider what would happen if the main connection failed. Depending on the importance of the phone service, options may include a secondary connection, mobile failover or call-routing arrangements.
4. Plan for power cuts
Traditional copper telephone lines could carry their own power, whereas a router and VoIP handset require local electricity. Identify critical phones and connected systems, then decide whether battery backup or an uninterruptible power supply is appropriate.
5. Review the telephone features your team needs
A digital migration is an opportunity to review how the business communicates. Consider:
- Number of desk and cordless handsets
- Remote and hybrid workers
- Call menus and departmental routing
- Voicemail-to-email
- Call recording requirements
- Mobile applications and softphones
- Reporting and call analytics
- Support for multiple sites
Avoid paying for functions the business will not use, but make sure the system can grow if more users or locations are added.
6. Create a staged migration plan
Agree the order in which numbers and services will move. Confirm number-porting arrangements, installation dates, staff training and how calls will be handled during the changeover. Critical equipment should be tested after migration rather than assumed to be working.
Questions to ask a telecoms provider
- Is our present broadband connection suitable for the proposed system?
- Can we retain our existing numbers?
- What equipment and installation are included?
- What happens during an internet or power outage?
- How quickly can users, handsets or sites be added?
- What support is available and what are the response times?
- What is the full contract term and monthly cost?
Review your business telecoms before the deadline
ABSS can help review your existing phone system, broadband, handsets and connected services before recommending suitable business telecom options.
Explore ABSS business telecommunications or request a free telecoms review.
Frequently asked questions
When is the PSTN switch-off?
Government guidance currently states that users of the Openreach PSTN need to migrate by 31 January 2027.
Will a business lose its existing telephone number?
Numbers can often be ported to a replacement service, but the arrangement should be confirmed with the provider before the migration.
Does VoIP work during a power cut?
Routers and most digital handsets require electricity. Businesses should consider battery backup, alternative routing or other resilience measures for critical communications.
Official guidance: GOV.UK – Telecommunications modernisation connectivity timeline.
