Just checked the ATO website, regarding your post and found this.
Income of individuals under the age of 18
What rate of tax applies to the income of minors? The tax rates featured in the table below apply in 2010-11 for minors who:
are Australian residents are not excepted persons, and have no excepted income. Other income Tax rates
$0 - $416 Nil
$417 - $1,307 Nil + 66% of the excess over $416
Over $1,307 45% of the total amount of income that is not excepted income
If the minor's taxable income is less than $67,500, they will get the low income tax offset. The maximum tax offset of $1,500 applies if their taxable income is $30,000 or less. This amount is reduced by four cents for each dollar over $30,000.
Example
Kris is 15 years old. She has no excepted income and $4,000 in other income. The tax payable on her income is:
$4,000 x 45% = $1,800
As Kris's eligible income is over $1,307 the total amount of income of $4,000 is taxed at 45%. As Kris's taxable income is less than $30,000, she gets the maximum tax offset of $1,500. The net amount payable by Kris is $300 ($1,800 - $1,500).
