Big switch off header with phone and laptop on office table

The Big Switch off 2025

In December 2025, UK telecommunications is set for its biggest shakeup in a generation. Known as ‘The Big Switch Off’, BT have announced that traditional telephony, including fixed lines and services in the Public Switch Telephone Network (PSTN) will be switched off and withdrawn from service.

Moving forward, UK businesses and consumers will be required to use a digital technology, such as Voice over Inter Protocol (VoIP).

If you’re one of the 70% of UK businesses still using a traditional landline system, time is running out.

In the following piece, we’ll discuss why it’s happening, the benefits of a VoIP system, and how we can help.  

PSTN, Integrated Services Digital Network (ISDN) and VoIP explained

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


PSTN is the UK’s traditional copper wire analogue telephone system. Its foundations were originally laid in the 1800s and despite continuous maintenance, it is essentially the same technology.


Considered a digital version of the traditional telephone line, the ISDN launched in 1986 and transfers voice and data via the PSTN infrastructure.

The new system launched to satisfy the UK’s need to make secure, long-distance voice communications.


Also known as IP telephony, VoIP means voice transmissions via the internet, rather than over traditional lines.

Why are PTSN and ISDN being switched off?

As our everyday lives become further reliant om mobile and internet communications, traditional networks are beginning to feel the strain.

Historically a reliable method of voice communication, PTSN technology is now considered dated and blighted by spiralling maintenance and operational costs.

Demand on an aging infrastructure, much of which originally designed in the 1800s, has seen the UK mirror many nations worldwide in turning their back on analogue.

Whilst the holes have previously been filled by IDSN, even this technology is starting to show its age. Rapid advancements in broadband technology have transformed voice communications and signalled the way forward for a complete digital solution no longer reliant on outdated analogue systems.

What’s the benefits of a VoIP solution?

Once it gets to December 2025, you won’t have a choice but to use a VoIP solution. However, that certainly isn’t a bad thing!

VoIP is fast becoming industry standard for voice communications. Increasing speeds, ease of use and cost-effective implementation make it the technology of choice.

Users avoid the physical limitations of analogue as calls are made via the internet. The scalability of the cloud-based software enables your phone system to seamlessly adapt to your business needs.

It’s important that we also remember one of the biggest after-effects of the covid pandemic; the rise of hybrid working. Internet-based voice technology simplifies the process as all employees are connect to one data network, as opposed to separate phone lines.

What does it mean for businesses still on ISDN or PSTN networks?

Unfortunately, BT’s decision to cease functionality of the networks means you’ll be left with no option but to switch.

For this reason, it’s important you have your house in order well before December 2025. We would highly recommend carrying out the following reviews:

  • Undertake an audit of your current connectivity procedures. It’s imperative you can effectively operate a VoIP system.
  • Identify areas that will be impacted (CCTV, alarm systems etc).
  • Use a comparison consultant to find the best solution on the market.

When should I switch?

Whilst you have until 2025, it’s advisable to start exploring your switching methods as soon as possible. Once you’ve undertaken the above reviews, it’s important to give yourself enough time to implement any required changes. Keep in mind the fact that you may also need additional time to find the capital required for any telephony upgrades required pre-switch.  

How can Great Annual Savings (GAS) help me?

We understand how stressful the migration of your business’ telecoms systems can be. Especially when you have a deadline enforced upon you. That’s why the team here at GAS are here to remove the burden and do the hard work for you.

We’ll analyse your current setup, identify your requirements, and analyse the market for a free, no obligation quote.

Simply get in touch via our online form or contact the team via 0800 130 3514.

For more business cost saving advice, please visit our hub.

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