One of the first things you do once you have arrived in Australia is to get yourself a Tax File Number (TFN) To make it a bit easier to understand, you could say it is the Australian version of your National Insurance Number. Applying for a TFN can be done easily on-line.
You cannot earn money in Australia without a TFN and having a TFN will also speed up any Centrelink payments that you may lodge, such as Family Assistance.
You should visit the Government website (by tapping the link above) to find out your rights and obligations regarding Tax File Numbers.
Australian Business Number (ABN)
If you are looking to work for yourself as a sole trader you will require registration for an Australian Business Number or ABN. It is essentially the equivalent of a TFN for the self employed. To find out whether you are entitled to an ABN and for assistance on applying for one - following this link to the Australian Tax Office website.