The Taxation concept of taxation is exactly as one would expect. Its intention is to cover the income entities receive from financial assets. In fact the actual legislative definition is quite readable.
Part 6 interpretation of the income tax assessment act has these definitions.
interest income, in relation to a taxpayer, means income consisting of interest, or a payment in the nature of interest, in respect of: (a) money lent, advanced or deposited; or (b) credit given; or (c) any other form of debt or liability;
passive income, in relation to a taxpayer, in relation to a year of income means: (e) interest income derived by the taxpayer in the year of income; or
This concept is quite straght forward and usually doesn’t create confusion. Anything that is “interest” according to the definition above is to be included as income and put into the relevant text boxes on the annual tax return (Usually titled Interest).