SIP Trunks and the 2027 Switch-Off
If your business runs on a SIP trunk, it’s reasonable to ask whether the switch-off applies to you. Much of the switch-off messaging is aimed at businesses still on analogue or ISDN lines, which can make SIP feel like a separate issue.
The short answer: SIP trunks themselves are not being switched off. However, that doesn’t mean nothing changes for you. There are a few things worth checking before 31 January 2027, and depending on what sits behind your setup, a simpler option may be worth considering too.
The reassurance
The PSTN/ISDN switch-off is about retiring the UK’s old copper-based phone network, with a hard cutover date of 31 January 2027. Because a SIP trunk already carries calls over the internet rather than copper, it isn’t built on the technology being decommissioned.
What to check
Being on SIP doesn’t automatically mean everything connected to your phone system is switch-off proof. A few areas are worth reviewing:
• What your SIP trunk is delivered over. Some SIP services still run over older-style circuits, such as certain leased lines or EFM connections, that sit closer to the legacy network than a standard internet connection. Confirm with your provider exactly what sits underneath yours.
• Other equipment still on copper. Alarm systems, card payment machines, lifts and fax lines are commonly overlooked. They sit separately from the main phone system but are often still connected via an analogue line that will stop working at cutover.
• Your provider’s own switch-off readiness. Not every SIP provider is prepared for the volume of migration activity expected as 2027 approaches. It’s worth confirming this directly.
• Capacity against actual usage. SIP trunk channels are often set up years ago and never revisited. The switch-off period is a natural point to right-size.
None of these are urgent on their own, but each is easier to address now than under time pressure next January.
Do you still need a PBX?
A SIP trunk exists to connect an on-site phone system, a PBX (private branch exchange), to the outside world over the internet instead of copper lines. It remains a sound fit for businesses that have invested in PBX hardware and have the resource, in-house or via a provider, to manage it.
For businesses reviewing their setup ahead of 2027, it’s worth considering whether that PBX still represents the best use of resource. For many small and medium-sized businesses, a simpler option exists: fully hosted virtual numbers and VoIP, where the phone system itself is cloud-based and managed for you. No on-site hardware, no PBX to maintain.
| Staying on SIP (with a PBX) | Hosted VoIP / virtual numbers | |
|---|---|---|
| On-site hardware | Required; a PBX is owned and managed | Not required; fully cloud-based |
| IT involvement | Ongoing management needed | Minimal; self-service portal |
| Best suited to | Larger businesses with existing PBX investment | Most small to medium businesses |
| Setup complexity | Higher | Lower |
| Scaling | Manual capacity planning | Flexible, on demand |
Neither option is incorrect; the right choice depends on what the current setup delivers. Where a PBX is functioning well and is manageable in-house, there’s little reason to replace it. Where it has become a burden, the switch-off is a reasonable point at which to simplify.
Staying on SIP
Where SIP remains the right fit, the priority is a modern trunk: flexible inbound and outbound channels, no long contracts, no setup charges, and no hidden usage policies. The aim is to exit the switch-off period with infrastructure suited to the business today, not a legacy system under a different name.
Reviewing your setup
Every SIP configuration differs, and the right next step depends on what’s currently in place. For a clear assessment ahead of the switch-off deadline, get in touch.
