Is registering for GST mandatory?
When you get an ABN, you don’t automatically qualify for GST. They’re two different things. Please contact the ATO and/or your accountant for further advice.
Typically, based on ATO’s requirements, “You must register for GST if you run a business or other enterprise and your annual turnover is $75,000 or more. If you run a business or other enterprise and your annual turnover is less than $75,000, registering for GST is optional.”
As you work for yourself, you are considered by the Australian Tax Office (ATO) to be a ‘Sole Trader’ (below is an image, so don't try to click on the 'register for GST' link!):
If you are registered for GST, all services you provide are GST payable. It is your obligation to keep and maintain accurate and complete records.
Learn how to register for GST by following this link.