Australian residents must declare foreign income. Worldwide income is subject to tax. You must declare all of your income, no matter what the source. Foreign income includes foreign pensions and annuities, foreign employment, foreign investment, foreign business, and capital gains on foreign assets.
Foreign income is subject to tax in the foreign country where it originated. In order to combat double taxation, there are a series of credits and exemptions – thanks to the Australian government’s tax treaties with more than 40 countries – that should help you get some of that money back.
If you are not an Australian resident, then you may not have to declare your income from non-Australian sources.