What is the PSTN switch-off?

The Public Switched Telephone Network is the copper-based system that has carried British phone calls for well over a century. Openreach is retiring it. Every phone line still running on it has to move to a digital, internet-based service before 31 January 2027.

This is not a marketing deadline invented by phone companies. It is a national infrastructure programme, and Ofcom has confirmed the date is final after one earlier extension from December 2025.

Who this affects

If your business has a traditional landline, an ISDN2 or ISDN30 line, or an on-site PBX connected to copper, you are affected. Roughly 2.8 million lines are still on the old network, and more than half a million of those are business premises.

You are also affected in ways that are easy to miss. Alarm panels, lift emergency phones, door entry systems, fax lines and some card terminals often sit on the same copper. They need checking too.

What happens if you do nothing

The line stops working. There is no grace period, because the exchange equipment itself is being decommissioned.

The practical risk is less dramatic but more expensive: leaving it late means joining a queue. Every one of those 2.8 million lines needs an engineer visit, a number port, or both, and there is a finite amount of installation capacity in the country.

What you move to

Most businesses move to a hosted VoIP system — your phone system lives with the provider, and your team uses desk phones or an app. Typical UK pricing is £8 to £18 per user per month.

Because that replaces both your line rental and your on-site system maintenance, most businesses end up paying 40–60% less overall. A ten-desk office commonly goes from around £520 a month to around £260.

Keeping your number

Almost always possible. Moving a number between providers is called porting, and every UK provider has to support it.

The catch is timing. Porting is a regulated process with its own timescales and cannot be rushed. Allow four to six weeks as a realistic planning figure, and longer for a large block of numbers. If your number is on your vehicles and your signage, start the conversation with months to spare rather than weeks.

What to do next

1. Find out what you are actually on. Your bill will say ISDN, PSTN, or analogue.
2. Count the lines and the extensions, including the ones nobody uses.
3. List the non-phone things on those lines — alarm, lift, card machine.
4. Check when your current contract ends.
5. Get quotes while providers are still competing for your business.

Check what you could save — eight questions, about a minute.