The ISDN and PSTN switch-off: what UK businesses must do now
Openreach is retiring the analogue and ISDN network. Here is the real deadline, what breaks, and how to migrate calmly.
By the Telappliant team
The UK's analogue telephone network is being switched off. Every business still running ISDN, analogue lines or anything plugged into them needs a migration plan, and the sensible time to build it was before the last twelve months of the programme.
What is actually happening
Openreach is retiring the Public Switched Telephone Network and ISDN, replacing them with IP-delivered voice over broadband or fibre. Stop-sell is already in force across the vast majority of exchanges, meaning you cannot order new analogue or ISDN services, and existing lines are being migrated to the end of the programme in January 2027.
The devices people forget
- Lift emergency lines and disabled refuge phones, which are a legal obligation
- Intruder and fire alarm signalling paths monitored by a third party
- Door entry systems and gate intercoms
- Card payment terminals still dialling out over analogue
- Fax lines used for a single supplier or health-sector workflow
- Legacy CCTV, telemetry and building management dial-out
Your three realistic options
Keep the phone system and feed it SIP trunks, which suits recent on-premise hardware with life left in it. Move to a cloud phone system, which is the default for most UK SMEs because it removes the hardware, the maintenance contract and the next migration. Or run a hybrid while a site or contract runs down. The right answer depends on the age of the system, not on the marketing.
Why the underlying connectivity matters more than the handsets
Voice over IP is only as good as the circuit under it. Before quoting handsets, check the fibre availability at each site, whether the circuit has a guaranteed fix time, and whether you need a second path or a 4G or 5G failover. A cheap broadband line carrying every call in the business is a false economy that shows up on your first bad Monday.
A migration plan that does not cause chaos
- Inventory every line, what it does and who owns it, including the ones nobody claims
- Check fibre and Ethernet availability at each address before choosing a platform
- Port numbers early, because porting is the part with genuine lead times
- Pilot one team, fix the call flows, then roll out site by site
- Replace or adapt non-voice devices in the same programme, not afterwards
- Keep the old system live in parallel for a short cutover window
What it costs to leave it late
Late migrations pay for expedited installs, temporary mobile workarounds and rushed hardware. Worse, the alarm and lift lines get discovered in the final fortnight, when compliance leaves you no room to negotiate. Everything about this project is cheaper with lead time.
