3CX is the most-deployed business phone software in the world. Roughly 350,000 businesses across 190 countries run their phones on it, including a substantial slice of UK SMEs. Most people first hear about it via their IT-support firm, an accountancy peer, or a quote from a managed provider. Almost none of those introductions explain what 3CX really is — they pitch a package wrapped around it. This page is the explanation.
3CX is licensed phone-system software. You buy a yearly licence from 3CX, you run the software somewhere (on a server in your office, a cloud VM you control, 3CX's own cloud, or a managed partner's cloud), you connect it to SIP trunks for outside calls, and you plug in handsets or use mobile and desktop apps. That's the whole thing.
That sentence already explains why 3CX is structurally different from RingCentral, 8x8, Aircall, Vonage, or Zoom Phone. Those are cloud services — you pay per user, per month, indefinitely, and the vendor runs absolutely everything. 3CX is software — you pay a per-system yearly fee that scales by capacity (not by user count), and you (or a partner) own the operational layer. Different economic model, different licence model, different relationship.
3CX comes in five editions. Most UK businesses live in PRO; small offices may sit on FREE; contact centres or anyone needing AI features want AI or Enterprise Plus.
| Edition | Who it's for | What it unlocks |
|---|---|---|
| SMB FREEUp to 10 users. Maximum 3 free subscriptions per account. | Tiny offices£0 | Basic call routing, mobile app, voicemail, single IVR. Lacks recording, queues, CRM integration, deep video. Fine for a 4-person solicitor's office until growth pushes it to BASIC or PRO. |
| BASICLicensed by Simultaneous Calls (SC), not user count. 5:1 to 7:1 users-to-SC. | Reliability tierFrom £250/yr | Better IVR, manageability, and reliability. Still no recording, no advanced queues, no CRM. Most UK SMEs skip BASIC and go straight to PRO — the gap in features doesn't justify the licence saving. |
| PROThe most common SME tier in the UK. | Standard SMEFrom £330/yr | Call recording, advanced call queues, deep CRM (Salesforce, HubSpot, Dynamics), reporting and wallboards, live chat, video, switchboard, hot desking, Microsoft Teams integration. The features most SMEs actually want all sit here. |
| AIAdds the AI suite plus enterprise routing features. | Contact-centre / Teams shopFrom £480/yr | PRO plus Teams direct routing, skills-based routing, AI call transcription, AI summaries and sentiment, AI receptionist. Worth it for inbound contact-centre operations or firms already standardised on Teams as their calling client. |
| Enterprise PlusAI tier plus pre-paid transcription minutes. | Heavy AI volumeAbove AI list | AI tier with bundled transcription minutes (30k at 8 SC, 60k at 16 SC). Relevant if your monthly AI transcription would otherwise exceed the pay-as-you-go floor; otherwise AI is the right tier. |
Prices are GBP, ex-VAT, snapshot May 2026 from 3cx.com/ordering/pricing/pricelist. 3CX runs an evergreen multi-year discount (10% off 1-year, 15% off 2-year, 20% off 3-year), so a 25-user firm on PRO at 8 SC pays ~£260/yr on a 3-year deal rather than £330/yr year-to-year. Hosting is a separate line — see 3CX hosting in the UK.
This is the part that trips up almost every UK SME owner who reads the 3CX pricelist for the first time. You don't pay per user. You pay for SC — Simultaneous Calls — which is how many calls the system can route at the same moment. 3CX's recommended user-to-SC ratio is 5:1 to 7:1, so a 35-user accountancy with normal call density typically needs 8 SC — not 24, not 32.
This matters because it's a common UK managed-provider sales tactic to quote 24 SC for 35 users. At PRO list that's £910/yr instead of £330/yr — a roughly 3× licence inflation the customer cannot easily check. 3CX's recommended user count for 8 SC PRO is up to 40 users. We write more about this on our honest-pricing page.
We have a full guide to the four hosting models with UK pricing, and a separate guide to evaluating UK 3CX partners.
Three things 3CX is sometimes confused with:
Yes. SMB FREE is genuinely free with no time limit. Maximum 3 free subscriptions per account, so a chain of 4+ small offices forces paid licensing. The constraint at FREE tier is features (no recording, no advanced queues, no CRM integration) more than the user cap.
You can buy 3CX licence and 3CX-hosted entirely self-service via 3cx.com. Most UK SMEs don't, because the licence is roughly 20% of the total managed-service value — the other 80% is the SIP trunks, handsets, porting, install, training, and ongoing support. Partners earn their margin on the operational layer, not the licence itself. We wrote a long answer to this if you want the structural reasons.
UK Openreach is closing the legacy copper-PSTN network in stages, completed nationally by end of January 2027 (originally December 2025; pushed once). If you're still on traditional analogue lines or ISDN30, you need to move to a SIP-based system before then. 3CX is one option; full-stack cloud services like RingCentral are another. See our PSTN switch-off guide.
Yes, on the AI tier (16+ SC). 3CX provides Teams direct routing so users can dial out and receive calls inside the Teams client while 3CX runs the call-routing logic underneath. The licence cost is usually lower than buying Microsoft Teams Phone Standard plus a UK calling plan from Microsoft directly.
We're a UK managed-3CX provider operating from Poole, Dorset and Canary Wharf, London. We sell the partner-managed model in box 4 above: licence, hosting, SIP, handsets, porting, training, support — one supplier, one bill, transparent line-by-line pricing on our honest-pricing page. Book a free audit and we'll quote against your real numbers, not a marketing-driven default SKU.