Procure Smart

The Big Switch Off: A Guide

Big switch off header with phone on office desk

In 2015, British Telecoms (BT) announced that from 2025, they would be switching off their Public Switched Telephone Network (PSTN) and Integrated Services Digital Network (ISDN) systems in a project nicknamed “The Big Switch Off”.

As with many similar UK infrastructure changes of such magnitude, that deadline has now been moved back to January 31st 2027.

Notably, a recent study showed that almost 70% of UK businesses polled still use landlines. More worryingly, 59.7% of them have no idea what the Big Switch Off is.  

Here at Procure Smart, we pride ourselves on our ability to simplify business decisions for our customers. In short, we like to make things as quick and easy as possible.

For this reason, we’ve produced a straightforward guide for ‘The Big Switch Off’. In the following piece, we’ll break down exactly what’s happening, how it’ll impact your business and what you need to do next.  Whilst the deadline has been extended, it still requires action from businesses utilising soon-to-be-outdated phone lines.

What is the Big Switch Off?

Before we start explaining the process, it’s probably best we explain the meaning behind some of the acronyms we’ll be using.


Previously the backbone of UK communications. It is an analogue system, meaning it traditionally transmits calls via physical lines (such as copper cables).


Introduced in 1986, it is a communication system that transmits voice and data over a digital line. Most importantly, ISDN uses the PSTN to operate.

VoIP (Voice over Inter Protocol)

A phone system that transmits voice and multimedia content exclusively over an internet connection. VoIP is often referred to as telephony.

From 2025, PSTN and ISDN will be switched off by BT and all calls subsequently routed over VoIP.

Why are they switching the networks off?

Simply put, the older networks no longer fully meet the requirements of a 21st century UK. Soaring mobile and internet communications, coupled with the rise of hybrid working, means demand is exceeding what traditional technologies were designed to deliver. 

Because of this, broadband speeds are now significantly faster than the traditional ISDN. As alluded to previously, the network is hampered by their reliance on the PSTN, an infrastructure dating back to the 1800s.

Rising maintenance costs and technological limitations continue to be significant limitations

The advancements of VoIP’s speed and reliability, coupled with lower integration costs for consumers, has left the technology as the preferred UK telecommunications solution moving forward.

Is it just the UK? Or are other countries following suit?

Migration to VoIP technology is not unique to the UK, in fact, many nations are already ahead in the process.

The Netherlands and Estonia have already switched their PSTN networks off and nations such as Japan, Germany and Sweden are already ahead of the curve in their plans.

What does the big switch off mean for businesses still on ISDN or PSTN networks?

Unfortunately, whether businesses like it or not, we’ll all need to make the switch before the revised Big Switch Off 2027 deadline day.

If you haven’t looked into it already, it’s important to start exploring a VoIP phone set-up for your business.  An audit of your current internet connectivity and reliability would be a great place to start. If you have concerns, it’s worth exploring the possibility of upgrading ahead of a move to VoIP.

Remember, it won’t just be your phone lines impacted.  Any services connected to the previous phone network (fax machines, CCTV and alarm systems) will also be affected.

How can Procure Smart help me?

We understand how stressful and anxiety-inducing everything we’ve discussed can be for businesses, especially those at the very beginning of the process.

To help, we have created a super-easy process for our experts to gather the necessary information to assess your costs and investigate savings, fast.

All we need is the following information and we’ll begin the quoting process:

      • An invoice detailing your current contract information.

      • The service you wish to switch (this can be done via our form check box).

      • Your contract end date (CED).

    Our dedicated account management team will oversee the whole process and deal with any queries from suppliers.

    Find out more about our hassle-free business telecoms switching service and read our team’s answers to some of our customers most frequently asked questions.

    Simply complete the form below to speak to one of our experts on a no-obligation basis.


    ***This blog was updated in June 2024***

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