In short: A PSTN switch-off checklist is a step-by-step plan for moving every analogue and ISDN line before Openreach closes the network on 31 January 2027. It covers auditing each line and device, choosing a replacement phone system, checking connectivity and power, porting numbers, testing alarms and special devices, and booking a migration date.
The dates that matter
Openreach stopped selling new analogue (WLR) lines across the UK on 5 September 2023. The switch-off of the analogue phone network (PSTN) is set for 31 January 2027, and Openreach's withdrawal of these services includes ISDN2 and ISDN30. BT Group reset the date in May 2024 from the original December 2025 deadline, and Openreach still encourages providers to move customers as early as possible.
For lines that have not moved in time, Openreach describes Emergency Voice Access as a temporary, voice-only service that keeps basic calls working for a limited period and may not support the calling features you use today. Treat it as a safety net rather than a plan, and work on the basis that every line, including ISDN, needs to move before the deadline.
This page is the practical checklist. For the full background on the switch-off, read PSTN switch-off 2027: a business guide or the PSTN switch-off: what businesses need to do from our sister company, Forever Communications Limited.
The checklist
Work through these steps in order. Most delays come from devices discovered late, so the audit matters most.
- Audit every line. List each phone number and line on every bill, then walk the building to find what is plugged into each one: phones, fax machines, intruder and fire alarms, lift emergency phones, door entry, card payment terminals, telecare units, franking machines, building management systems and remote monitoring.
- Match lines to bills. Note the provider, account number, contract end date and any broadband that runs over the same line. Look for lines you pay for but no longer use, and lines nobody can explain.
- Choose the replacement phone system. Decide whether to keep your PBX on SIP trunks, move to a hosted system such as Forever UC or hosted 3CX, move to Microsoft Teams Phone, or choose BT Cloud Voice. Our ISDN replacement options page compares them.
- Check connectivity. Digital voice runs over your internet connection, so confirm the broadband or leased line at each site has enough upload capacity, a router that can prioritise voice, and a back-up path if calls are business-critical.
- Plan for power cuts. Analogue phones were powered by the exchange; Openreach points out that digital phone lines need power at your premises, so phones, routers and network switches need mains power. Decide which devices need battery back-up and how staff will reach emergency services if the power fails, for example on a mobile.
- Plan number porting. Collect a recent bill for each account and list every number to keep, including DDI ranges. Our number porting guide explains the process and the common reasons ports are rejected.
- Test special devices. Ask your alarm, lift, door-entry, telecare and payment-terminal suppliers whether each device works on a digital line, needs an adapter, or should move to a mobile (SIM-based) or IP connection. Test each one after migration.
- Set a migration date. Book the work for a quiet period, move one site or one group of lines at a time, and allow time for a rejected port to be resubmitted.
- Update emergency addresses. Make sure every number has the correct address registered with the new provider so emergency services are sent to the right place.
- Close the old lines. Cease the old services only once every number, device and alarm is confirmed working, and keep a record of what was moved.
A simple line audit template
Use one row per line or number. A spreadsheet with these columns is enough for most organisations.
| Column | What to record |
|---|---|
| Number | The number on the bill, including any DDI range |
| Location | Site, building and room, or where the line enters the building |
| Connected device | Phone system, alarm, lift, door entry, card terminal, fax, telecare and so on |
| Provider and account | Who bills it, the account number and the contract end date |
| Broadband on the line? | Whether internet service runs over the same line and would be affected |
| Replacement | New phone system, SIP trunk, digital line, adapter or mobile connection |
| Owner and test result | Who signs it off, the date it was tested and the outcome |
For alarm panels, lift lines, door entry and other special lines, see alarm and special lines, which explains the options in more detail.
Choosing what to move to
The switch-off is a good moment to review the phone system itself, not only the lines. A few questions narrow it down quickly:
- Is your current PBX still supported and does it have SIP? If so, SIP trunks replace the ISDN or analogue lines and keep your handsets and features.
- Do your staff already live in Microsoft 365? Microsoft Teams Phone puts calls in Teams; Forever Teams does it while keeping your numbers.
- Do you want a managed system with apps and optional desk phones? Look at Forever UC, hosted 3CX or Webex Calling.
- Do you want BT as a single supplier? Our BT Cloud Voice overview explains where it fits.
The cloud phone system comparison sets the platforms side by side, and the business phone systems buyer's guide lists the questions to ask any supplier.
How we help
We run the checklist with you rather than handing it over. That includes:
- A line and device audit across your sites, with a clear list of what needs to move and what can be ceased
- A vendor-neutral recommendation for the replacement phone system
- Connectivity checks and, where needed, new broadband or leased lines through Forever Group
- Number porting, handset set-up and staff training
- Co-ordination with your alarm and lift maintainers so special lines are tested before the old lines go
There is no charge to talk it through. Contact us and tell us how many sites and lines you have.
Why choose your cloud phone system with Forever Systems
We are vendor-neutral. Forever Group supplies and supports several cloud phone platforms, so we recommend the one that fits how your organisation works rather than the one we happen to sell.
- Side-by-side comparison of hosted 3CX, Microsoft Teams Phone, Forever UC, Forever Teams and Webex Calling for your users
- Contact centre and call recording options matched to your call volumes and CRM
- Number porting, handsets and set-up handled for you, including the move off analogue and ISDN lines
- Connectivity checked so call quality is right from day one
- UK support for moves, adds, changes and faults
- For BT Cloud Voice, see our BT Business Partner site cloudvoice.cloud
We work with businesses, schools, charities and public sector organisations. We do not sell consumer phone services.
Want a vendor-neutral cloud phone system comparison and quote?
Tell Forever Systems what you need and we will come back to you by email with options, not a hard sell.
Contact usFrequently asked questions
When is the PSTN switch-off in the UK?
Openreach's switch-off date for the analogue phone network (PSTN), including ISDN services, is 31 January 2027. It stopped selling new analogue lines across the UK on 5 September 2023, and the 2027 date replaced the original December 2025 deadline.
What happens to my phone line after 31 January 2027?
Analogue and ISDN services are being withdrawn. Openreach describes Emergency Voice Access as a temporary, voice-only service for lines not switched in time, which may not support the features you use today. It is a safety net rather than a replacement, so plan to move every line, including ISDN, before the deadline.
Will my alarm work after the PSTN switch-off?
Some alarms work on a digital line and some do not. Ask your alarm company whether your panel needs an adapter, an upgrade or a move to a mobile or IP connection, and test it after your line is migrated.
Do digital phones work in a power cut?
Not on their own. Digital phones, routers and network switches need mains power, unlike old analogue phones. If you need phones during a power cut, add battery back-up to the key equipment and have a mobile available for emergency calls.
Do I need to change my phone system for the PSTN switch-off?
Not always. If your current PBX is supported and can use SIP, SIP trunks can replace the old lines. If it cannot, or it is near the end of its life, a hosted system or Microsoft Teams Phone is the usual alternative.