2025 and the ISDN switch off is around the corner. Are you ready?

Stop burying your head in the sand!  The ISDN switch off is really happening and 2025 is the end date.

We appreciate that everyone has more than enough to think about dealing with Covid-19.

However, as BT will be switching off all ISDN lines by December 2025, maybe it’s the perfect opportunity  to upgrade your phone system, utilising latest technologies and taking advantage of a hosted IP telephone system.

Over the last decade or so, there has been a huge global shift to cloud products.  This includes internet-based phone systems (meaning, voice services that are provided over a broadband connection, with the phone system sitting in the cloud.)

BT have therefore made the massive decision to cease long established ISDN lines and migrate all services to use VoIP (Voice over Internet Protocol.)  It does make perfect sense to make this decision, as BT were faced with the costly upkeep of old legacy networks.

Timeframe to 2025 Switch Off

Well, the phasing out is most definitely underway.   See Openreach timeline

  • From 2018, the announcement was made that any products that were reliant on the PSTN (Public Switched Telephone Network) would stop being sold within five years
  • In June of last year, certain areas in the UK were being used for testing the migration and withdrawal process
  • In September 2023 – the intention is to stop selling products for the PSTN
  • And, December 2025 – all  ISDN lines will be withdrawn –  end of life.

The task is on a monumental scale. It will also affect every single business and home, and all Critical National Infrastructure (i.e. Police, Fire, NHS, Electricity, Gas Water etc.)  There are no exceptions.

So what will the big switch off mean to you and your business? 

Well, first off  you will need to assess your current system to see if you use any fixed lines and establish whether your current system is compatible with using newer technologies.  So, if your system is or can be SIP enabled (Session Initiation Protocol) or you are already using a hosted phone system then no need to worry!

However if you have a traditional phone system using a premises based PBX and ISDN lines, then you really should start looking around for alternative methods to support your business communications before 2025.  Numbers on fixed telephone lines will need to be ported to a new VoIP provider.

Comparison between ISDN and VoIP 

FlexibilityLacks flexibility to support expansion and costly to make changesTotally in control, easily scalable, add or take away extensions as required
Savings More costlySubstantial savings on calls and line rentals and no maintenance costs
Business ContinuityDiverting calls is a slow processCalls can be re-routed easily when disaster strikes
Future There is no futureModern, future proof and robust. Convergence for voice an data
Compatibility Not compatible with the latest Unified Communication solutionsCan easily incorporate a unified communications solution for a powerful business system


Making the move now will give you a huge armoury of features, great functionality and flexibility.  Your employees and customers alike, could be enjoying our ultimate unified communications telephone system, keeping your business totally connected and moving in the right direction, especially  during these uncertain times.

We have plenty of solutions and can also integrate our phone system neatly with Microsoft Teams.  Bringing you, your team and customers together, boosting productivity and service levels.

Merlin’s systems utilise the most highly resilient networks and with over 15 years experience of hosted solutions, we can offer plenty of advice and talk you through exactly what you need to know and what you need to do.

With only four years left before the switch off in 2025,  we imagine you will want to start the ball rolling now.

If you have any questions for us please call us on 0800 8778810 or contact us

The Merlin Team