"PSTN Switch-Off 2027: What Your Business Needs to Do Before the Deadline"

BT is switching off the UK's traditional telephone network on 31 January 2027. That's roughly six months away. Around 500,000 business premises are still on copper lines, and the cost of staying on one is already rising fast.

If your business is one of them, this post covers what the switch-off actually means, what the migration involves, and why leaving it until autumn is a genuinely bad idea.

What is being switched off

The PSTN (Public Switched Telephone Network) is the copper telephone infrastructure the UK has used since the Victorian era. ISDN is a digital variant of the same network, commonly used by businesses with multi-line phone systems or older PBX setups.

Both go away in January 2027. Openreach, which owns the physical network, has been decommissioning exchanges on a rolling basis since 2023. Once your exchange closes, calls have to travel over broadband instead of copper. There's no extension and no workaround.

If you're already on a VoIP system, you're fine. If you're on PSTN or ISDN lines, you need to move.

The cost pressure is landing right now

This is not only a January 2027 problem. Openreach has been raising the cost of Wholesale Line Rental throughout 2026 specifically to push businesses off copper. The increases:

• April 2026: +20%
• July 2026: +40%
• October 2026: a further +40%

By November, copper line rental will have roughly doubled compared to what it cost at the start of the year. You're paying more every quarter for a service that's being shut down.

If the migration cost has felt like a reason to delay, the maths are shifting.

Who is most at risk of getting caught out

Migrating standard phone lines is straightforward. The businesses that run into real problems are the ones that don't realise they have other devices connected to a copper line.

Intruder alarms and fire panels. Many security systems use a PSTN line to dial out when triggered. These can't just be swapped to VoIP without checking compatibility with the alarm panel and your monitoring company. Some panels need replacing, not just reconfiguring.

Card payment terminals. Older PDQ machines sometimes use a phone line as a fallback route for transactions. Worth confirming with your payment provider before the line goes dark.

Lift emergency phones. Buildings with passenger lifts are legally required to have an emergency communication line. A large number of them still run on PSTN. This one often catches building managers and facilities teams completely off guard.

Legacy PBX systems. On-site phone systems more than 10 years old frequently connect to ISDN trunks rather than SIP. Those systems either need a SIP adapter or full replacement.

None of these are difficult to solve. But they all take time, and finding out in November that your alarm panel is not compatible with VoIP is a very different situation to finding it out in July.

What the migration actually involves

For a typical SMB with a handful of phone lines and no legacy complications, the process is:

1. Audit what you have — phone lines, numbers, and any connected devices
2. Choose a VoIP system and provider
3. Port your existing numbers to the new system (5–10 working days)
4. Install IP handsets and configure extensions
5. Test thoroughly, then cut over

On a modern system like UniFi Talk, the setup is clean. Desk phones connect to your network switch over standard cabling, calls are managed locally, and your numbers port across without any change visible to the people calling you.

For a small office with no complications, the whole process typically takes two to four weeks from first conversation to go-live. The number porting is usually the longest part of the critical path.

Why Q4 is the wrong time to start

October feels comfortable ahead of a January deadline. It isn't.

Number porting takes up to 10 working days, longer if there are complications with your current provider. Equipment sometimes has lead times. Getting an engineer booked in the run-up to Christmas is harder than it sounds. And every provider and installer in the country will be handling a surge of last-minute migrations from businesses that left it too long.

We saw the same pattern during the 3G network shutdown. Most businesses who could have sorted it in spring were scrambling in the final weeks. Providers got overwhelmed, timelines slipped, and some businesses ended up with disruption they could have avoided completely.

The businesses starting this month will have a clean cutover in September or October, with time to deal with anything unexpected. The businesses starting in November will be in a queue.

What to do this week

Start by finding out what you actually have. Call your phone provider and ask whether your lines are PSTN, ISDN, or already on SIP/VoIP. They can tell you immediately.

If you're on copper, find out:

• How many lines you have and which numbers are in use
• Whether any alarms, payment terminals, or other equipment connects through those lines
• What phone system you're running and roughly how old it is

That's enough to have a useful conversation with an installer about what migration looks like for your specific setup, and how long it's likely to take.

If you're based in West Yorkshire and want us to take a look, we're happy to carry out a free audit and give you a straight answer on what's involved. No obligation, no sales pitch. Get in touch here.

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Airedale Tech designs and installs VoIP telephony systems for businesses across West Yorkshire. We handle PSTN and ISDN migrations for offices, multi-site operations, and businesses with legacy PBX systems — including those with alarm systems, lift lines, and other non-standard connections.