What is VoIP?

VoIP stands for Voice over Internet Protocol. Instead of your phone call travelling down a dedicated copper line, your voice is converted into data and carried across your internet connection, the same way your email and website traffic are.

That one change explains almost everything about modern business telephony. Calls are no longer tied to a physical line in the wall, so a phone number can follow you to a new office, a home desk or a mobile app without an engineer visit.

A VoIP setup has three parts: a connection, a service and endpoints. The connection is your broadband, which now carries your calls as well as everything else. The service is the hosted phone system or SIP trunk that routes calls and holds your features. The endpoints are the handsets, headsets or softphone apps your team actually uses.

Call quality depends mostly on the connection. A reliable internet service with enough upload capacity, a router that can prioritise voice traffic, and a network that is not congested will sound identical to a traditional line. A poor connection will not, which is why any honest VoIP conversation starts with a broadband check, not a handset brochure.

The practical benefits are straightforward. You can keep your existing numbers, add a user in minutes rather than waiting for an engineer, and pick up calls on a desk phone, laptop or mobile app with the same number. Features such as voicemail to email, call recording, auto attendants and hunt groups are standard rather than optional extras.

There is also a deadline behind all of this. The UK's analogue and ISDN networks are being retired, with the final withdrawal of the old line services planned for the end of January 2027. Businesses still renting analogue lines need a replacement plan before then, and VoIP is the replacement for the overwhelming majority.

VoIP problems are almost always network problems. Calls that drop or sound robotic usually point to an undersupplied connection, a router that treats voice the same as file downloads, or an office WiFi setup that was never designed for telephony.

The fix is planning: check that the broadband can carry calls plus everything else, configure traffic prioritisation, and give desk phones a wired connection where possible. Done properly, VoIP is boring in the best way. It just works.

If you want the fuller version, our guide to VoIP covers the technology in more depth, and our SIP and VoIP service page explains how we deliver it. If you would rather just find out whether your lines are affected by the switch-off, the PSTN checker tool gives you an answer in a couple of minutes.