Two-way SMS is text messaging in which the customer can reply and the reply reaches the business. For a trade business, that usually means a customer answers a booking reminder with a single letter, and the job is confirmed or moved without a phone call. Two-way SMS needs a number that can receive messages, and in Australia it also sits under the Spam Act 2003 and, from 1 July 2026, the ACMA SMS Sender ID Register.
This article explains how two-way SMS works, how it differs from one-way messaging, what the Australian rules require, and how air-con cleaners and other mobile trades use it for confirmations, rescheduling and repeat work.
TL;DR
- Two-way SMS lets customers reply to a business text. One-way SMS only sends.
- Replies need a number that can receive messages. Most alphanumeric sender IDs (a business name in place of a number) cannot receive replies.
- Since 1 July 2026, alphanumeric sender IDs used to message Australian recipients must be registered with the ACMA, or messages may be marked unverified or blocked.
- Under the Spam Act, marketing texts need consent and a working unsubscribe. The business stays responsible even when software sends the message.
- The best trade uses are narrow: confirm, reschedule, and share arrival or access details.
Table of Contents
- What two-way SMS is and how it works
- One-way and two-way SMS compared
- Dedicated numbers and alphanumeric sender IDs
- The ACMA SMS Sender ID Register
- Spam Act rules for two-way messages
- Where two-way SMS fits in a trade business
- What to check before choosing a two-way SMS setup
- Our view on two-way SMS
- Booking, reminders and payments in one place
- Setting up two-way SMS in a trade business
- FAQ
- Sources
What two-way SMS is and how it works
In a one-way setup, a business sends a text and the conversation ends there. In a two-way setup, the message is sent from a number or channel that can also receive. The customer replies, the platform captures the reply, and it either triggers an action (such as confirming a booking) or lands in an inbox for a person to answer.
There are three parts to the process:
- A sending identity. This is usually a dedicated mobile or virtual number. It can also be a short code, but dedicated numbers are the common choice for small businesses.
- Inbound routing. The platform receives replies sent to that number and attaches them to a customer record or job.
- Rules or people. Replies are either read by staff or matched against keywords such as C for confirm and R for reschedule.
The second part is where many small businesses lose value. If replies go to a phone nobody checks, or to a number that is not connected to the calendar, the customer response creates extra work rather than removing it.
One-way and two-way SMS compared
| Feature | One-way SMS | Two-way SMS |
|---|---|---|
| Customer can reply | No | Yes |
| Sender | Often an alphanumeric sender ID | Dedicated number |
| Typical use | Alerts, simple notices | Confirmations, rescheduling, questions |
| Opt-out by reply | Not reliable | Possible with a reply code |
| Staff effort | Low, but replies go nowhere | Low if replies are automated |
One-way messages are suitable for notices that need no response. Any message that asks the customer to do something, such as confirm a time, is better sent two-way.
Dedicated numbers and alphanumeric sender IDs
An alphanumeric sender ID shows a name, such as a business name, at the top of the message instead of a phone number. It looks credible, but most sender IDs cannot receive return messages, because there is no phone number for the reply to be routed to. A guide to two-way SMS from an Australian bulk SMS provider makes the same point: a dedicated number is needed to receive replies.
The practical choice for a trade business is:
- Dedicated number when the customer is expected to answer. This covers confirmations, reschedules and questions.
- Alphanumeric sender ID only for one-way notices where a reply is not expected and an opt-out is provided another way.
The two can be combined, but a message that tells customers to reply cannot come from an ID that does not accept replies.
The ACMA SMS Sender ID Register
From 1 July 2026, texts sent with an organisation's name at the top of a message must use a registered sender ID. The requirement applies to alphanumeric sender IDs used to send messages to Australian recipients, regardless of where the message originates. Messages sent with unregistered IDs may be marked as unverified or blocked by carriers.
A few practical points follow:
- Registration is made through the messaging provider or platform, and it helps to have Australian Business Register details current. Twilio's overview of the register notes that updating ABN information can speed registration up.
- The same source lists format limits: a sender ID is at least 2 and no more than 11 characters long.
- A business that sends only from a standard mobile or virtual number does not use a branded sender ID, so the register is not the main concern. The Spam Act still applies.
Sole traders using a booking platform generally do not register the ID themselves. They should confirm with the platform how the sender identity is handled and whether messages show a number or a name.
Spam Act rules for two-way messages
Two-way SMS is a convenient way to get customer replies, but it does not change the legal position. The ACMA's guidance is that marketing messages need the recipient's consent before they are sent, and this applies even when another party sends them on the business's behalf.
Service messages and marketing messages
A booking confirmation or a reminder with a time and address is a service message. Adding a promotion, such as a discount on the next clean, can turn it into a commercial message. The ACMA also states that automated 'welcome journeys' are not exempt from the law because they often contain commercial content. Keeping service messages to the service is the simplest approach. A fuller walkthrough is in the MyAirCare guide to SMS marketing laws for Australian tradies.
Unsubscribe requirements
Commercial messages must include a functional way to opt out. According to the ACMA, the request must be actioned within 5 working days, and the mechanism must stay working for at least 30 days after the message is sent. It must not charge a fee beyond standard SMS rates, and it must not require the recipient to log in or supply extra personal information.
This is where two-way SMS helps. A reply code such as STOP works on a dedicated number. The same ACMA page warns that asking customers to reply to a message from an alphanumeric sender ID usually fails, because the ID cannot receive the reply and the unsubscribe is not functional. An alternative, such as a 1800 number, is needed in that case.
Consent records
The ACMA expects businesses to keep records of consent. Its statement of expectations on consent covers who gave consent, when and how, and favours express consent over inferred consent. For a cleaner, the booking itself can record this: the customer ticks an option for reminders and offers when booking online, and the date is stored with the customer record.
Responsibility stays with the sender
The ACMA has penalised a business that described promotional texts as information only. In the Latitude Finance case, a $1.55m penalty followed messages that were labelled informational but promoted products. The practical lesson for small operators is that using a third-party platform does not move the legal responsibility away from the business that sends the message.
Where two-way SMS fits in a trade business
Two-way SMS works best when it asks for one simple action. A common pattern is a message that asks the customer to reply C to confirm or R to reschedule. An Australian trade SMS provider describes reminders sent 24 hours and 2 hours before a job, with customers confirming or rescheduling by reply.
For air-con cleaning, these are the common uses.
Booking confirmation
The message is sent when the booking is made. It states the date, the arrival window, the address and the service booked. It asks for a reply only if something is wrong. A structure for this is set out in the guide to a booking confirmation SMS for trade teams.
Reminders with a reply
A reminder the day before reduces the chance of an empty trip. It should say what the technician needs, such as clear access to the indoor unit, and offer a reply to confirm or move the time. Example wording is in these appointment reminder templates. A case study from an Adelaide automation firm reports that automated two-step SMS reminders cut no-shows at a physio clinic. It is a different industry, so the figures should be read as an illustration rather than an air-con result.
Rescheduling
A customer who replies R should receive a link or a short list of available times, rather than a message that waits for staff. This keeps changes inside the calendar and prevents double bookings.
Service reminders for repeat work
Air-con units need regular cleaning, so a message sent months after a job is a natural prompt to book again. Because this is commercial, consent and an opt-out are needed. The approach is covered in service reminder automation for trade businesses.
Missed calls and quotes
Tradies on a roof or under a house often miss calls. An automatic text to the caller, which they can answer, keeps the lead. See how missed call text back works for Australian trades. Quote follow-ups also suit a reply format, as described in the quote follow-up guide for air-con cleaners.
What to check before choosing a two-way SMS setup
| Question | Why it matters |
|---|---|
| Does the message come from a number that can receive replies? | Without it, replies are lost and opt-outs fail. |
| Where do replies go? | They should attach to the customer and job, not to a personal phone. |
| Can keywords trigger actions? | Confirm and reschedule replies should update the calendar. |
| How is opt-out handled? | The Spam Act requires a working method. |
| Is the sender ID registered, if one is used? | Required from 1 July 2026. |
| What does each message cost? | Costs scale with job volume. |
On cost, one trade-focused SMS provider says credit-based pricing can start at roughly 6 to 8 cents per message, with no monthly fee. A sole trader sending a few confirmations and reminders per job can estimate monthly cost by multiplying jobs by messages per job by the per-message rate. Rates vary by provider and should be checked on the day.
A stand-alone SMS tool needs a person or an integration to trigger each message. When messaging is built into the booking system, the booking triggers the text and the reply updates the job. The MyAirCare article on cutting admin time with three technology changes covers this in a wider context, and the comparison of field service apps lists what to look for in the software.
Our view on two-way SMS
MyAirCare was designed around the way air-con cleaning businesses run day to day, and the same few problems come up in that work: missed calls, double bookings, customers who are not home, and slow weeks with no repeat work.
We think two-way SMS is worth using for a small number of tasks and not for everything. Confirm, reschedule and remind cover most of the value. Long conversations are better on a phone call.
We also think the tool should do the compliance work where it can. A reminder that goes out automatically after a booking is easy to set up and easy to forget, so consent and opt-outs belong in the booking flow, not in a separate checklist. The business still carries the legal responsibility, which is why consent is recorded at the time of booking.
Finally, messages should be short and about the job. Customers answer a message that asks for one thing. Messages that mix a reminder with a sales pitch are more likely to be ignored and to raise Spam Act questions.
— Lewis
Booking, reminders and payments in one place
MyAirCare is booking and management software for Australian air-con cleaners. It covers online booking pages, automated job reminders, customer records, quotes and invoices, a calendar for teams, and a mobile app for rescheduling and on-site payments, with card payments through Stripe. There is a Free plan at $0 per month, supported by booking fees, and MyAirCare Pro at $199 per month. The plans are listed on the MyAirCare pricing page, and the MyAirCare home page describes the full platform. The platform also lists an AI phone agent add-on, for which no price is published.
Setting up two-way SMS in a trade business
- List the messages. Booking confirmation, day-before reminder, reschedule offer and a post-job follow-up are enough to begin.
- Choose a number that can receive replies. Avoid a name-only sender ID for any message that asks for a response.
- Write each message around one action. For example: reply C to confirm or R to reschedule.
- Record consent at booking. Store the date and the method.
- Add an opt-out to commercial messages. Test that it works from a handset.
- Route replies to the job record. Replies should update the calendar or alert a person.
- Review monthly. Check confirmation rates, opt-outs and any replies that did not match a keyword.
For after-hours enquiries, the guide to after-hours bookings with privacy in mind covers what to do with replies that arrive when no one is working.
FAQ
What is two-way SMS and how does it work?
Two-way SMS lets a business send a text and receive the customer's reply. The business sends from a number that can receive messages, the platform captures the reply, and either a person or an automatic rule responds. In trade work, a reply such as C or R often confirms or moves a booking.
Can a business receive replies to a text sent from a business name?
Usually not. Most alphanumeric sender IDs cannot receive return messages, according to the ACMA's spam guidance. A dedicated mobile or virtual number is needed for replies, and for a reply-based unsubscribe.
Does the sender ID register apply to tradies?
It applies to any business sending texts to Australian recipients with an alphanumeric sender ID, from 1 July 2026. A business that sends from a standard number does not use a branded sender ID. Anyone unsure should ask their SMS or booking platform which identity is used.
Is B2B texting legal in Australia?
Business-to-business messages are still covered by the Spam Act if they are commercial. The ACMA says consent is needed before marketing messages are sent, along with a working unsubscribe. Legal advice is appropriate for edge cases, such as messages to an existing client's staff.
Do reminders need an unsubscribe link?
A plain service message, such as a time and address for a booked job, is different from a commercial message. Once a message promotes a service, the ACMA's unsubscribe rules apply. Many operators add a simple opt-out to all reminders to avoid doubt.
Sources
- SMS Sender ID Register, ACMA
- Australia sender ID registration, AWS End User Messaging SMS
- What you should know about Australia's new SMS Sender ID Register, Twilio
- Avoid sending spam, ACMA
- Telemarketing and e-marketing: common issues and mistakes, ACMA
- Consent expectations for businesses using direct marketing, ACMA
- Email and SMS unsubscribe rules fact sheet, ACMA
- Latitude Finance pays $1.55m penalty for spam breaches, ACMA
- Two-Way SMS for Business, Australia Bulk SMS
- SMS for Tradies and Trade Businesses in Australia
- Cut Physio No-Shows With AI, AI Adelaide