ISDN Switch Off
ISDN switch off: the 2027 deadline explained
Every ISDN2 and ISDN30 circuit in the UK is withdrawn by 31 January 2027. Here is the timeline, what stops working on the day, and how long a move to the cloud actually takes.
Direct answer
When is the ISDN switch off date?
The ISDN switch off date is 31 January 2027. That is the point at which ISDN2 and ISDN30 services are switched off nationally, alongside the analogue PSTN. In practice many businesses lose service earlier: exchanges are migrated area by area, and providers move customers off ISDN months ahead of the final date.
New ISDN circuits stopped being sold in September 2023, so you cannot add channels, move an ISDN30 to a new building, or renew a contract past the deadline. Whatever your ISDN does today is the most it will ever do.
Timeline
The ISDN withdrawal timeline
September 2023
Stop-sell nationwide. No new ISDN2 or ISDN30 lines, no extra channels, no site moves.
2024 – 2026
Exchange-by-exchange migration. Providers give notice and move customers to digital services.
31 January 2027
Final switch off. Any remaining ISDN circuit stops carrying calls.
Impact
What stops working when ISDN is switched off
It is rarely just the phones — ISDN usually sits behind a mix of equipment nobody has audited in years.
Your main number
Inbound calls to the ISDN circuit stop connecting. Numbers must be ported before the line goes, not after.
The on-site PBX
The PBX itself may be fine, but it needs SIP trunks underneath it — or replacing with a cloud system.
Alarms, lifts and door entry
Anything that dials out over the old network stops reporting. These need checking well before your migration date.
Card machines and fax
Legacy dial-up terminals need a broadband or mobile route, or a replacement device.
Cost of waiting
Why leaving it late gets expensive
Number porting takes days, not minutes, and engineer availability shrinks the closer we get to 2027. Firms that wait tend to pay twice: once for a rushed migration, and again for the calls missed during a cutover booked at short notice. Moving early also stops you paying ISDN30 line rental for channels you no longer use — most businesses cut their monthly bill on the day they leave ISDN behind.
If you want the full replacement options rather than the deadline detail, read the ISDN2 and ISDN30 replacement guide or the wider PSTN switch off replacement options.
Next step
A migration plan takes one phone call
We survey what your ISDN does today, list the numbers and connected equipment, then give you a fixed plan with a cutover date. Free number porting and free setup, and a Leeds-based team on 0113 522 0000.
See ISDN replacement pricingFAQ
Frequently asked questions
Further reading: when the ISDN switch off happens and how to plan it, the risk of delaying your migration and switch-off planning across multiple sites. In Yorkshire? See Leeds business phone systems.
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