Dedicated numbers vs shared numbers vs sender IDs

When you send a business text in Australia, the "from" the customer sees is one of three things: a dedicated number that is yours alone, a shared number pooled across many senders, or an alphanumeric sender ID that shows a word like your business name. They behave very differently, and picking the wrong one means either paying for something you do not need or losing the ability to have a conversation. Here is a plain comparison so you can choose once and get it right.

Dedicated number: your own two-way line

A dedicated number is a mobile number that belongs to your business and nobody else. It is the standard way SMS365 sends, and for most small businesses it is the right default.

The defining feature is that it is two-way. Customers can reply, and the reply comes back to you in the same thread. That one property is behind most of what makes SMS useful:

• Appointment and job confirmations customers can reply YES to.
• Invoice reminders they can answer with "paying Friday", which the AI assistant can record as a promise to pay.
• Keyword opt-ins, where a customer texts JOIN to your number to subscribe.
• STOP and START handled in the same thread, with the opt-out logged to a consent ledger.
• A consistent number customers recognise and can save to their contacts.

Hi Dave, confirming your service is booked for Thu 17 Sep, 8 to 9am. Reply YES to confirm or call if the time doesn't suit. Mackay Plumbing.

That message only works because Dave can reply. On a dedicated number he can. The cost is modest, around $10 a month on SMS365, and for a two-way line you control, that is the easy call. This is why two-way matters so much that it has its own piece: two-way SMS and why it matters.

Shared numbers: cheap, and you get what you pay for

A shared number is one that many businesses send through, pooled together. It looks cheaper because you are not paying for a number of your own, and for pure one-off broadcasts it can do the job. But the trade-offs are real and worth understanding before you save the ten dollars.

• Replies are a mess. If a customer replies to a shared number, the system has to guess which sender they meant, and often the reply goes nowhere useful. You lose the conversation.
• No consistent identity. The number can change between sends, so customers cannot save it or recognise you, and a message from an unfamiliar number is more likely to be ignored or reported.
• Shared reputation. If another business on the same shared number sends spam and gets the number flagged, your messages can be caught in the fallout. You are trusting strangers with your deliverability.

For a business that wants a relationship with its customers, a shared number is a false economy. SMS365's model is a dedicated number precisely because the conversation and the consistent identity are where the value is, and a shared number throws both away to save a small monthly fee.

Alphanumeric sender ID: your name on screen, no replies

An alphanumeric sender ID replaces the "from" number with up to eleven characters of text, usually your business name, so the message shows as coming from "CoastCafe" rather than digits. It looks polished and puts your brand on the customer's screen.

The trade-off is the mirror image of a shared number's. A sender ID is strictly one-way. A customer cannot reply to a word, so you lose two-way conversation and you cannot handle STOP through the same channel, which means you need an unsubscribe link instead. There is also a step you cannot skip: in Australia, alphanumeric sender IDs must be registered on the ACMA SMS Sender ID Register before you can use them, which takes time and is not something you set up the afternoon before a campaign. That process is explained in alphanumeric sender IDs and the ACMA register explained.

CoastCafe: Winter sale starts Fri, up to 40% off in-store. Details and unsubscribe: coast.cafe/sale

A sender ID is the right tool for a specific job: a pure one-way broadcast to a large audience where brand recognition on screen matters more than replies, and opt-outs are handled by a link. A one-off sale announcement to ten thousand people is the classic fit. For everyday conversational messaging it is the wrong tool, because it silences the customer.

How to choose

The decision comes down to one question: does the customer need to reply?

• If yes, or even maybe, use a dedicated number. Confirmations, reminders, invoices, support, opt-ins, anything conversational. This is most small business messaging, and it is why the dedicated number is the SMS365 default.
• If it is a genuine one-way broadcast to a big list, and brand-on-screen is worth more than replies, a registered sender ID fits, as long as you have planned for the registration lead time and set up an unsubscribe link.
• A shared number is rarely the right answer for a business building relationships. The saving is small and the costs, lost replies, no identity, borrowed reputation, are large.

Plenty of businesses run both a dedicated number and a registered sender ID: the number for the day-to-day two-way traffic, the sender ID for the occasional large broadcast. That gives you conversation where you need it and a branded blast where it helps, and it is a sensible setup once your volume justifies the sender ID registration.

Whatever you choose, the same honesty applies to delivery: SMS365 marks a message "sent" when it is handed to the carrier and "delivered" only when a real receipt comes back, so you are never told a broadcast landed when it might not have. For what a dedicated number and a registered sender ID each cost, the pricing page has the current figures, and if you are weighing it up on cost specifically, what SMS costs in Australia breaks down the per-message and per-number side of the bill.