The ISDN Switch Off was announced back in 2017, yet it has been given relatively little publicity. That was, until September 2023, when a national stop sell on ISDN-reliant products and service was put into place by Openreach, which prevented anyone buying new ISDN-based products or modifying existing services.

The UK Integrated Services Digital Network (ISDN) is being switched off in December 2025. Though you’re probably already aware of that by now – especially if you’ve had a read of any of the other articles on this site.

Now, as the ISDN Switch Off date looms large on the horizon, many businesses are struggling to put a strategy together and still have questions that need to be answered.

But don’t worry, we’ve taken the time to identify the five key questions that SMEs are asking about the ISDN network, and what the December 2025 deadline means for their business. Read on and start to plan your route to a successful digital switchover.

What does the ISDN Switch Off mean for SMEs?

The ISDN Switch Off isn’t just about your phones. There are plenty of systems – and acronyms – that are jostling for attention. For SMEs, the Switch Off affects phone lines, broadband connections, payment devices, door entry systems and much more.

Does your phone system rely on a digital phone line such as ISDN2, ISDN30 or PSTN Multiline? How about your broadband connection? Does it run on ADSL2, a standard for delivering internet connectivity through telephone connections?

Then there are your wider business systems and services to think about. Do you rely on a Single Analogue Exchange Line for Process Data Quickly (PDQ) handheld payment devices, franking machines, emergency alarms, lift lines, help point systems, door entry systems, fax machines or even care home alarms?

If you have any of these services linked to the ISDN, they will simply stop working. And that will place your business in a whole world of trouble.

Make a start today. Run a device audit, and make sure you scrutinise everything in your business that could make use of analogue lines to function. And don’t let the acronyms confuse you – your existing supplier(s) should be able to tell you if you’re on analogue lines. Once you’ve got that sorted, you can put together a solid migration plan.

How much will the ISDN Switch Off cost my business?

If you have a PSTN or ISDN contract, you’ll need to switch over to an Internet Protocol (IP) telephony solution. There will be costs involved, but you’re also going to see plenty of benefits.

What’s more, most Voice over Internet Protocol (VoIP) phone packages work on a per-user pricing model, so you can save money in the long run by prioritising the connections you need.

You have a wide range of choices as well. If VoIP isn’t right for you, then take a look at Session Initiation Protocol (SIP) trunking; the digital method of making and receiving phone calls and other digital communications over an internet connection. This replacement technology can connect the majority of existing systems to the new public network. Then there’s Unified Communications (UC), hosted telephony and hosted contact centres.

There’s also a chance you’ll be able to pick up some cheaper deals, as Openreach will incentivise suppliers to migrate more customers onto future-proofed products. However, it’s a double-edged sword, as increased demand could see VoIP prices getting pushed up as the deadline gets closer – another reason to act now and not wait!

For something as fundamental as connectivity, you want to make sure you have the right deal in place for your specific needs, so don’t focus on cost alone.

Does my business even need a landline?

For the overwhelming majority of businesses, a ‘landline’ telephone number is still worth the investment.

Despite the proliferation of mobile phones, having a traditional landline phone number is still regarded as an indicator a business is real and trustworthy. A landline number gives the perception of an established, credible company. Even if you have it set to divert to your mobile, your customers won’t know.

Embracing the VoIP approach, to what we’d traditionally think of as landlines, offers much better call quality and options compared with mobile phones. Although many mobile phones now use Voice over Long-Term Evolution (VoLTE) and internet calling to improve reception, they don’t have the capacity to handle high call volumes.

As newer technologies develop and become more widely used, the role of the landline is not truly dying with the Switch Off of the copper lines, it’s just evolving. Rather than being the primary point of contact for your customers, it now sits within a larger range of communication options.

Can I keep the same business number after ISDN Switch Off?

The good news is that you can keep your old PSTN phone number when you switch to digital voice services and full-fibre broadband. There could be a few exceptions around some ISDN special features, but in most cases, it will be a fast and easy process.

That means you won’t have to worry about losing touch with existing customers, or need to alter any of your marketing materials, print and digital collateral or vehicle livery.

What should I look for in a provider when switching phone lines?

There are a lot of UK VoIP providers out there, so make sure you do your research. As we’ve already mentioned, don’t focus solely on price.

Of course, you want a great deal, but that doesn’t necessarily mean using the cheapest provider you can find. Look for a combination of expertise, experience, value for money, reliability, good customer service, financial stability and clear communication.

Independent review websites are a great place to start, and you can also ask your business contacts for recommendations. But remember that the best provider for the ISDN switch over isn’t the same for everyone. Your business will have its own unique requirements. Make sure the supplier you choose offers a solution that fits your needs, rather than a standard off-the-shelf package.

Taking your next step to ISDN Switch Off

Now you have the answers to the top five ISDN Switch Off questions asked by SMEs, make your move.

There’s a lot to do by December 2025, but now is a good time to start.

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