The UK PSTN switch-off: what your business needs to know for January 2027

The UK's traditional phone network is being switched off. If your business still runs on analogue phone lines or ISDN, the deadline you need to know about is 31 January 2027. That's when Openreach withdraws PSTN (Public Switched Telephone Network) services across the country.

Here's what that actually means, what your options are, and how to work out whether you need to act now or later.

What's actually switching off

Three things:

Analogue PSTN lines (POTS). The classic single copper phone line running into a small office.
ISDN2 — the two-channel digital service common in small businesses.
ISDN30 — the higher-capacity variant used by PBX-connected phone systems in most UK SMEs and mid-market firms.

If any of those describe how your calls get in and out of the building, you're in scope.

What's not switching off

Copper broadband as such isn't going anywhere overnight. Openreach has confirmed carve-outs for vulnerable customers extending through 2030, and copper-based broadband (VDSL, G.fast) continues in many areas.
VoIP and SIP-based calls are unaffected. If your phones already run over the internet using SIP trunks or a hosted UC service, you don't need to do anything for the switch-off itself.
Mobile networks are separate and not affected.

Openreach's actual timeline

Stop-sell already complete. Openreach stopped selling new PSTN and ISDN services regionally through 2023-2025.
Migration window through 2026 — Openreach ran a large-scale "digital voice managed exit" through 2026 for customers who hadn't moved themselves.
31 January 2027 — full retirement of PSTN and ISDN.
Vulnerable-user carve-outs push some copper endpoints into 2030 following a BT and Openreach policy shift in late 2024.

If you haven't heard from your line provider yet, you will.

The decision tree

Roughly three shapes of business, three routes.

If you've already got hosted phones or SIP trunks

Nothing to do. Confirm with your provider in writing if you want the reassurance.

If you've got a physical PBX on-premise with ISDN lines coming in

You have a real decision to make. There are three routes:

Route A — Keep the PBX, swap the incoming lines. Convert your ISDN service to SIP trunks. Your PBX carries on serving your existing handsets. This is the least disruptive route and often the cheapest short-term. Not every PBX supports SIP trunks natively, and some need a licence upgrade or a small gateway device. Ask your maintainer or IT provider whether your specific model can take SIP.

Route B — Move the whole thing to hosted UC. Microsoft Teams Phone, Zoom Phone, RingCentral, 8x8, Webex Calling and similar. Your handsets get replaced (or in some cases the existing SIP handsets get re-provisioned against the new service). Higher upfront work, lower long-term maintenance, subscription per user.

Route C — A hybrid. Some businesses run hosted UC for most users and keep an on-prem PBX for specific reliability-critical rooms or sites with poor internet. Legitimate pattern, especially in manufacturing and healthcare.

If you've got a very old system and you're not sure

Get a current view of it before you decide. Book an audit with your existing maintainer or an independent adviser. What matters:

Which PBX model and firmware are you on?
Which handsets are attached to it?
How many concurrent calls do you actually need?
Where are your lines coming in from (which provider, which product)?

That view unlocks the answer. Without it you're guessing.

What this means for your handsets

The handsets themselves are separate from the switch-off. A wired phone that plugs into a PBX will keep working after 31 January 2027, as long as the PBX itself has been re-plumbed to accept SIP trunks instead of ISDN.

But if you're changing the PBX at the same time (Route B, hosted UC), the old handsets often can't come with you. Some SIP handsets can be re-provisioned to a hosted platform. Digital handsets (like the Avaya 1408, 1416, 9504 or 9508 that connect to an Avaya IP Office over DCP) will not work with anything other than a compatible Avaya PBX. When the PBX goes, those handsets go.

That's where a lot of businesses end up with cupboards full of old desk phones they can't reuse. It's the point in the migration where a lot of firms come to us.

Timing

If your ISDN contract renews before Jan 2027, that's your natural decision point. Providers have been actively contacting customers through 2026 with migration options. Don't leave it until December — the queue for engineering work in the run-up to the deadline will get heavy.

If you're already in the middle of a hosted-UC migration, you probably don't need to worry about the deadline itself. Confirm with your provider that the ISDN lines are being ceased as part of the project.

If you're on Route A (keeping the PBX, converting to SIP trunks), your provider should have a defined process. It's often quicker than people expect — a couple of weeks from order to cut-over.

About the old handsets

If your migration ends with a stack of old desk phones — Avaya, Cisco, Mitel, Poly, Yealink — you don't have to skip them. There's still a secondary market for most models, and there's a compliance obligation on wiping them properly before they leave your premises.

We collect, wipe, and issue a Certificate of Sanitisation for desk phones. See What we buy — desk phones for how it works.