Check that you're eligible for an ABN. Only companies registered under the Australian Corporations Law and those doing business in Australia are entitled to an ABN. The Australian Taxation Office has an entitlement tool on their website which helps individuals decide if they can apply for an ABN.
Find a registered tax agent in your area. The Tax Practitioners Board registers agents on behalf of the Australian Government and their website has a search facility to help you find a local agent. You're not obliged to use a tax agent, but an experienced agent will help your business deal effectively and securely with the tax authorities through the electronic commerce interface system, known as ECI, which requires specific software.
Provide your tax agent with the information and documents required to apply for your ABN. You will need to provide proof of your legal name and current address, full details of your business and proof that it is registered in Australia.
Apply for a tax file number, known as a TFN, if you don't already have one. Although it's not obligatory to have a TFN when you apply for an ABN, it may delay your application if you don't have one. You can apply for a TFN at the same time you apply for your ABN but only if you are a company, partnership or trust (not an individual). Individuals should apply through their tax agent.
Register for Goods and Services Tax, known as GST, if your annual turnover is more than AUD$75,000. You can't register for GST until you have your ABN but you can apply to register at the same time as your ABN application.