Please refer to the ATO for information on starting and running your own business.
If you carry on an enterprise in Australia as a sole trader, you can apply for an ABN for your business and use this number for all your business dealings. You can obtain an ABN by applying for it through the ATO via the Australian Business Register website. There is no fee for applying but if you use a tax agent to complete an application for you they may charge for their services.
You can also register for goods and services tax (GST) if you carry on an enterprise, on the ABN application form. You must be registered for GST if your annual GST turnover is $75,000 or more.
Note: The above information should not be considered legal, accounting or tax advice. We recommend you speak with an accountant or tax advisor or your financial advisor and we expressly disclaim any responsibility for any action taken or not taken based on this information.