For most UK small businesses, the best small business PBX today is a cloud (hosted) PBX: it typically costs roughly £8–£15 per user per month, needs no on-site hardware, and scales up or down instantly. On-premises and hybrid systems still suit specific cases — but with the PSTN switch-off, cloud is now the default choice for under-20-user teams.
What a PBX actually does for a small business today
A PBX (Private Branch Exchange) is the system that routes calls inside your business and connects you to the outside world. It handles the things you take for granted — extensions, call transfers, hold music, voicemail, an auto-attendant ("press 1 for sales") and hunt groups that ring several people at once.
The big shift is that a modern PBX is software, not a metal box in a cupboard. A cloud PBX runs in a data centre and reaches your handsets, laptops and mobiles over the internet using VoIP (Voice over IP). That means a five-person firm can have the same call-handling features that once needed an expensive on-site exchange.
For a small team the practical wins are simple: one business number that follows staff between desk, home and mobile; call recording for compliance; and an auto-attendant that makes a micro-business sound established. You can read more about the underlying technology on our cloud hosted PBX page.
Cloud PBX vs on-premises vs hybrid for small teams
There are three broad models, and for most small businesses the choice is genuinely straightforward. A cloud (hosted) PBX puts everything in the provider's data centre — you just plug in handsets or use a softphone app. An on-premises PBX keeps the call-control hardware on your site, which you own and maintain. A hybrid PBX splits the two: on-site equipment for calls, but with cloud features and SIP trunks bolted on.
As a working guide, cloud suits almost every business under 20 users because there is no capital outlay, no maintenance and no single point of failure on your premises. On-premises makes sense mainly where you have very specific integrations, poor internet, or an existing system you have already paid for. Hybrid is a transitional choice — useful if you want to protect an investment in on-site hardware while gradually moving to the cloud.
One caveat: cloud PBX depends entirely on your connectivity. If your broadband is unreliable, fix that first — a backup connectivity link or a business-grade line will do more for call quality than any phone system feature.
Best small business PBX options in the UK compared
Rather than name a single "winner", it helps to think in categories, because the right system depends on where your team works and what you already use. Below are the mainstream options UK small businesses actually choose.
Microsoft 365 users often get the best value by adding voice to software they already pay for. If your team lives in Teams, turning it into your phone system removes a separate app and a separate bill — see our Teams phone system service for how that works.
- Microsoft Teams Phone — best if you already run Microsoft 365; calls, meetings and chat in one app, with a Teams calling plan or SIP connection for external numbers.
- Dedicated hosted PBX (e.g. Gamma, 3CX-based platforms) — best for businesses that want proper call-centre features, wallboards and flexible call routing without Microsoft lock-in.
- Virtual phone system / app-only — best for sole traders and very small teams who just need a professional number and voicemail on mobiles, with no desk phones at all.
- On-premises IP-PBX — best only where you have specific compliance, integration or connectivity reasons to keep hardware on site.
- Hybrid PBX with SIP trunks — best when replacing legacy ISDN gradually while keeping some existing handsets.
Costs: setup, per-user and the hidden charges
Cloud PBX pricing is refreshingly predictable. As a working guide, expect roughly £8–£15 per user per month for a hosted seat, often including UK landline and mobile call bundles. Entry-level virtual/app-only plans can start nearer £5 per user. Setup is usually low — sometimes a small provisioning fee, sometimes free — because there is no on-site installation.
On-premises is the opposite shape: a larger upfront cost (commonly £1,500–£6,000+ for a small system including handsets and licensing), plus ongoing maintenance and eventual replacement. You also still pay for SIP trunks or lines to carry calls. Over a three-to-five-year period, cloud usually works out cheaper for small teams once you include support and hardware refresh.
Watch the hidden charges on any quote: number porting fees, minimum contract terms (often 24–36 months), charges for call recording or CRM integration as add-ons, and the cost of desk handsets if they aren't included. Ask whether the SIP trunk or calling plan covers your typical call volume, or whether you'll drift into per-minute charges.
What features actually matter for under-20 users
It's easy to be sold a feature list you'll never use. For a small team, a handful of features do the real work. An auto-attendant and clear call routing make you sound organised. Hunt groups and ring groups stop calls going to voicemail. Mobile and softphone apps let staff work from anywhere on the business number — the single most useful feature for hybrid working.
Call recording matters if you handle payments or regulated advice, and it's worth checking whether it's included or an add-on. Voicemail-to-email, presence (seeing who's available) and simple call reporting round out what most small firms need. Integration with your CRM or Microsoft 365 is valuable but only if you'll actually use it — don't pay for it speculatively.
Reliability is a feature too. Ask about the provider's uptime record, and whether calls automatically failover to mobiles if your internet drops. Pairing a hosted phone system with sound connectivity and telecoms is what separates a system that works from one that frustrates.
Is the PSTN switch-off forcing your decision?
Yes — and it's the single biggest reason to act now. Openreach is retiring the traditional PSTN (Public Switched Telephone Network) and ISDN, with the national switch-off scheduled for the end of January 2027. After that, analogue and ISDN phone lines will stop working, and every business will need to make calls over IP instead.
In practice this means any small business still on old copper lines must move to a VoIP-based system — which, for most, means a cloud PBX. The good news is you don't have to wait for a forced migration; moving early lets you choose the system and timing that suit you, and often cuts your line rental in the process.
If you're planning a move, treat it as one project rather than two: sort your internet, then your phone system. Our team can scope both together — see business phone systems in London or get in touch to plan your switch before the deadline crowd.
Our recommendation for most UK small businesses
For the majority of small businesses under 20 users, a cloud PBX is the best choice: low upfront cost, predictable per-user pricing, no hardware to maintain, and it's already switch-off-ready. If you run Microsoft 365, start by evaluating Teams Phone before adding a separate platform, because it may cost less and simplify your stack.
Choose on-premises only if you have a specific reason — a large existing hardware investment, unusual integrations, or connectivity you can't yet improve. Choose hybrid as a bridge, not a destination. And whatever you pick, get your connectivity right first, because call quality lives or dies on the line underneath.
If you'd like an honest comparison mapped to your headcount and how your team works, contact us and we'll recommend the option that fits — not the one with the longest feature list.