Do I Need a Phone System or Just a VOIP Line? A Plain English Answer

Someone has told you that you need a phone system. Or you have been looking at options and the terminology. PBX, hosted PBX, SIP lines, VOIP, extensions. Is making something that should be simple feel complicated. This guide cuts through it. By the end you will know whether you need a full phone system, a basic VOIP line, or something in between, and roughly what each option costs for a small Australian business.

The short answer for most businesses with one to five staff: you need a hosted phone system, and it is cheaper and simpler than you think. For a sole trader or freelancer who just needs a dedicated business number: a basic VOIP line with voicemail is probably enough. The decision turns on one question, which we will get to shortly.

What a PBX Actually Is

A PBX, or private branch exchange, is the system that sits between your phone numbers and your staff. Think of it as a traffic controller. When a call comes in, the PBX decides where to send it. Which phone to ring, in what order, and what to do if nobody answers. It handles hold music, after-hours messages, call menus, and voicemail.

Twenty years ago, a PBX was a physical box in a server room, expensive to buy and requiring an IT person to maintain. Today, the same functionality is delivered as software running on a provider's servers. You do not buy it; you subscribe to it as part of a VOIP phone plan. This is called a hosted PBX, or cloud phone system.

The cost of a hosted PBX for a small business is typically $20 to $35 per user per month with unlimited local and national calls included. That is roughly what a traditional landline costs per month, but with a full phone system included.

What a Basic VOIP Line Is

A basic VOIP line is a single phone number that delivers calls to one device. A softphone app on your mobile, a desk phone, or a computer. There is no routing logic, no ring groups, no auto-attendant. You get a number, calls ring on one device, and you answer them.

This is sometimes called a SIP line or a direct SIP account. A SIP line (Session Initiation Protocol line) is essentially a virtual phone line delivered over the internet, the same way a traditional phone line was delivered over copper. The cost is typically $5 to $15 per month for the line, plus call charges. No PBX, no extensions, no management.

The One Question That Decides It

Here is the question: will more than one person in your business ever need to take a call at the same time?

If yes, you need a hosted phone system. Two staff taking simultaneous calls requires two lines. A hosted phone system manages this automatically, rings phones based on rules you set, and handles the second call properly if the first line is busy.

If no. You are a sole trader, you are the only person answering calls, and you just want a business number that is not your mobile. A basic VOIP line is enough. Add a voicemail service and you have everything a one-person operation needs for $10 to $20 per month.

What a Hosted Phone System Gives You That a Basic Line Does Not

Even at entry-level pricing, a hosted phone system includes features that change how your business handles calls. These are not optional upgrades. They come standard with most AU VOIP business plans.

Ring groups allow multiple phones to ring at once when a call comes in, rather than just one desk. This means two staff can potentially answer the same inbound call, and whichever picks up first handles it. For a small team taking inbound enquiries, this alone is worth the difference between a line and a system.

After-hours routing sends calls to a voicemail, a message, or a mobile number outside business hours. Without it, a customer calling after 5pm either gets a ringing tone with no answer or an ISP generic voicemail. With it, they hear your business name and get a clear next step.

Voicemail to email delivers missed call recordings to your email inbox. You never check a handset voicemail again. For a small business owner who is often out of the office, this is a significant practical improvement.

An IVR, or interactive voice response system, is the automated menu callers hear when they ring your business. "press 1 for sales, press 2 for support." You do not need this if you have one or two staff. You might want it if your business has multiple departments or if you want to route calls differently at different times.

What Each Option Costs for an Australian Small Business

Basic VOIP line (sole trader or single user): approximately $10 to $20 per month for a single number with voicemail, plus per-minute or per-call charges. Suitable for a one-person operation who just needs a dedicated business number.

Hosted phone system (2 to 10 staff): approximately $20 to $35 per user per month with unlimited local and national calls, ring groups, voicemail to email, and a basic auto-attendant. A three-person team pays roughly $60 to $100 per month for a fully functional business phone system. Hardware (desk phones) is separate, typically $80 to $300 per handset as a one-off cost.

Most reputable AU VOIP providers include the hosted PBX in the per-user price. You are not buying the phone system separately and then paying for lines on top. The plan price includes both the service and the system that manages it.

Do You Actually Need a Desk Phone?

No. A softphone app is a phone application that runs on your computer or mobile. It connects to your VOIP service exactly the same way a desk phone does. For businesses where staff are often mobile or work from home, softphones can replace desk phones entirely. Many AU VOIP providers offer a softphone app as part of the plan.

If your business operates from a fixed location and you want the reliability and audio quality of a dedicated handset, a desk phone is worth the hardware cost. For a mobile or home-based operation, a softphone removes the hardware expense. Our desk phone vs softphone guide covers the trade-offs in more detail.

The NBN Phone Port: What Most Small Businesses Are Currently Using

Many Australian small businesses are currently taking calls through the green phone port on their NBN modem. This uses an ATA (analogue telephone adapter). A device built into the modem that lets a traditional analogue handset make calls over the internet. Your ISP controls this service and it includes the phone number.

The ATA port delivers one phone line. If your line is busy when someone calls, they get an engaged tone. There is no voicemail to email, no ring groups, no after-hours routing. You cannot take two calls at once. For a business that is growing or that misses calls regularly, this is a meaningful commercial limitation, not just a feature gap. See our guide on NBN phone options for Australian businesses for a full breakdown of what each tier delivers.

What Most Businesses Get Wrong

The most common mistake is assuming a phone system is complex or expensive. Most small businesses are surprised to find that a three-person hosted phone system costs less than their current mobile plan per person, and includes capabilities they did not know were accessible at that price point.

The second mistake is starting with the hardware. Buying a desk phone before choosing a provider creates compatibility questions that are easily avoided by going in the other direction. Choose your provider first, confirm they support your intended phone model, then buy the hardware they recommend. See our guide on setting up a new IP phone in Australia for the step-by-step process.

The third mistake is buying a full phone system when a basic line is genuinely enough. If you are a sole trader who primarily works via mobile and just wants a second number that rings to your phone, a $15 per month VOIP line with voicemail is a perfectly reasonable solution. Do not over-engineer it.

Your Next Steps

Answer the one question: will more than one person in your business ever need to take a call at the same time? If yes, get a hosted phone system plan from an AU VOIP provider. If no, a basic VOIP line is enough.

For a hosted phone system: use our phone system sizing wizard to work out how many lines and what features you need. Then get a recommendation from an AU provider who can confirm your requirements and provide a plan price.

For a basic VOIP line: contact an AU VOIP provider and ask for a single-user plan with voicemail to email. Most will have you set up within a day.

If you have confirmed that a hosted phone system is the right call for your business, our comparison of the best phone system for small business in Australia walks through the top AU-hosted options by price, concurrent call capacity, and which ones are easiest to set up without an IT team.

Once you have decided that a phone system is right for your business, the next question is cloud-hosted versus an on-premise box. For most small businesses, the cloud option wins on cost and flexibility. The full trade-off breakdown is in our cloud phone system vs office phone system comparison.

If you decide that desk phones are worth having, hardware choice matters. Not every phone registers cleanly with every AU VOIP provider. Our guide to the best SIP desk phone in Australia covers the most reliable models for AU VOIP networks, including which ones support auto-provisioning and what to avoid.