Also finding relevant information is always helpful and the eWombat search facility (an Australian product) on this site can help, it even offers benefits other search mechanisms can't.  For example, it only searches websites relevant to your needs and searches a number at a time to save you time and effort or the risk of missing something important.  The sites searched include the ATO, Centrelink, ATO Law, ASIC, Australasian Legal Information Institute, and State Revenue offices. 

However, eWombats move more slowly than things like Googles but they tend to bring back more relevant local information.

Australian business number (ABN)
The Australian Business Number (ABN) is a single identifier for all business dealings with the tax office and for dealings with other government departments and agencies.

Business activity statement (BAS)
Businesses use an activity statement to report and pay a number of tax obligations, including GST, pay as you go (PAYG) instalments, PAYG withholding and fringe benefits tax. Activity statements are also used by individuals who need to pay quarterly PAYG instalments.

Capital gains tax (CGT)
Capital gains tax (CGT) is the tax you pay on a capital gain. It is not a separate tax, just part of your income tax. The most common way you make a capital gain (or capital loss) is by selling assets such as real estate, shares or managed fund investments. Managed funds also distribute capital gains you must report.

Division 7A
Division 7A may apply to private companies that make tax-free distributions to shareholders or shareholders' associates in the form of payments, loans or debts forgiven.

People with disabilities
What you need to know if you have a disability or you are managing the tax and superannuation affairs for someone who has a disability.

Source:  Australian Taxation office