Cloud PBX. From your carrier.

A cloud PBX is a complete phone system that a provider runs for you. Extensions, voicemail, the auto-attendant, and call routing all live on the provider’s servers instead of a box in your closet. Your desk phones and softphone apps register to the provider over the internet. The provider handles everything from call control to the hand-off to the telephone network. Cloud PBX, hosted PBX, and virtual PBX all name the same thing: a PBX phone system that someone else runs. The industry uses all three.

Most buyers never see that a typical cloud PBX has two companies inside it. One is the platform that sells you seats. The other is the carrier underneath that actually touches the phone network. SIPNEX collapses those layers. The cloud PBX systems we host run on our own FCC-licensed carrier network. That is why every call leaves signed at A-level attestation, not at whatever level the platform’s upstream produces.

Prefer to run your own PBX software? The same network is available as SIP trunking for any PBX.

A cloud-based phone system has four moving parts. None of them sit in your office.

1. Your phones register. Each desk phone or softphone app signs in to the provider over the internet using SIP, the Session Initiation Protocol. Its extension is now live wherever the phone is.
2. The provider’s PBX handles call control. When someone dials, the PBX decides where the call goes: an extension, a ring group, the auto-attendant, or voicemail. Your routing rules live there, not in a box on a wall.
3. Audio travels in real time. Voice moves as RTP packets, the Real-time Transport Protocol. A G.711 call uses about 85 kbps in each direction once headers are counted, so bandwidth is rarely the issue. Jitter and packet loss are what hurt call quality.
4. The carrier hands the call to the phone network. On SIPNEX, that carrier is us. We attach an A-level signature under our own STIR/SHAKEN certificate and deliver it to the far end.

A traditional PBX is a hardware phone system on your premises. It connects to copper lines or a PRI circuit, and someone on your side keeps it alive. A cloud PBX moves the whole system to a provider. Here is how the two compare on the points that decide most migrations.

The cost savings of a cloud PBX come from what you stop buying. There is no PBX hardware to purchase, no maintenance contract that renews higher every year, and no PRI circuit to rent while the incumbents retire copper. You pay per extension, and that price covers the system. The spending you keep is your internet connection and the phones themselves.

It is not automatically cheaper, though. A paid-off PBX with a competent maintainer has no subscription at all. What ends it is usually the hardware reaching end of life, or the copper it plugs into being retired. Our guide to traditional PBX vs cloud PBX covers the decision honestly, including when to keep the box.

Business hosted PBX pricing on SIPNEX is per extension, from $6.99 a month, with every feature included; calling bills at the published carrier rates. That is the whole model. There is no contract and no feature tier. Call recording, the auto-attendant, and ring groups come with every extension, because we are not reselling anyone’s platform.

UCaaS platforms price differently. As of September 2026, RingCentral’s RingEX costs $20 (Core), $25 (Advanced), or $35 (Ultra) per user per month, billed annually. Month-to-month, those tiers are $30, $35, and $45. Its Customer Engagement Bundle is quote-only. Features such as CRM integrations and reporting arrive on the higher tiers. Zoom Phone publishes separate annual and monthly per-user rates, with phone bundled into its Workplace tiers. None of this is hidden, but you have to read the fine print. How cloud PBX pricing actually works is worth five minutes before you sign anything.

Unified communications platforms (UCaaS) bundle chat, meetings, and a phone system into one seat, and they sit on somebody else’s carrier. A cloud PBX from the carrier is the phone system layer itself. For business communication that is mostly calls, the differences below are the ones that show up on your bill and your caller ID.

Every feature below comes with every SIPNEX extension.

• Auto-attendant (IVR). The menu that answers: press 1 for sales, 2 for support. It routes callers without a receptionist.
• Ring groups. One number rings a set of extensions at once or in order, so the first free person picks up.
• Time-based routing. Day calls go to the front desk. Night and weekend calls go to voicemail or an on-call extension.

A cloud PBX that serves a business is a multi-line telephone system (MLTS) under FCC rules, and two federal laws apply. Kari’s Law mandates direct 911 dialing: a user must reach 911 with no prefix or access code, such as dialing 9 first. It also requires the system to notify a central location, on-site or off-site, the moment a 911 call is made. The rules apply to systems installed after February 16, 2020.

Section 506 of the RAY BAUM’S Act adds dispatchable location. Every 911 call must carry the caller’s validated street address plus the suite, floor, or room a responder needs. The deadlines have passed: January 6, 2021 for fixed devices and January 6, 2022 for non-fixed and off-premises devices such as softphones.

SIPNEX provides enhanced 911 in the 50 US states. Every deployment gets a Registered Location on file before it goes live, and each site gets its own. When a worker moves, you send the new address and we update the record. The direct-dial and on-site alert settings sit on the operator side, and we flag all three layers at turn-up. Our E911 for VoIP service page and E911 guide go deeper.

1. Count extensions and list your numbers. Every person or room that needs a phone is an extension. Every number you want to keep goes on the porting list.
2. Check the network. Budget about 85 kbps each way per call, turn on QoS for voice, and disable SIP ALG on the router. It is the router feature that rewrites SIP and breaks registrations.
3. Pick your phones. Existing SIP desk phones re-register to SIPNEX. Softphone apps cover laptops and mobiles. Analog phones need an ATA.
4. Register E911 addresses. One Registered Location per site, with suite or floor detail. Remote workers register their home address.
5. Port the numbers. Local numbers move in 7 to 14 business days. The old service keeps working until the port completes, so you cut over on your schedule. Number porting explained covers the paperwork.

A cloud PBX is the right tool for an office. It is the wrong tool for a call center. Predictive dialers such as VICIdial need raw trunk capacity, control over codecs and caller ID, and per-minute pricing rather than per-seat fees. That is SIP trunking, and SIPNEX sells that too.

There is a middle path. If you want your own FreePBX but not the server, SIPNEX FreePBX hosting runs the software for you with our trunks already connected. And many operations run both: hosted extensions for office staff and SIP trunks for the dialer floor, on one carrier. Hosted PBX vs SIP trunking lays out the decision.

The seat price tells you little. These five questions sort any provider in one call.

1. Who signs our outbound calls, and at what attestation level? A carrier answers at once: we do, A-level. A platform has to describe an upstream.
2. Which features cost extra? Ask about call recording, analytics, and integrations by name, and which tier each one lands on.
3. What is the monthly price without annual prepay? Headline rates often assume you pay for the year up front.
4. Who handles E911 and number porting? Both should have a named process and a person, not a ticket queue.
5. Can we run a dialer on it? If you run or plan a call center, read the acceptable-use policy first. RingCentral’s, for one, prohibits auto and predictive dialing.

Our guide to cloud PBX providers sorts the market into carriers, platforms, and resellers.