tax in australia

ok i know i am gonna sound stupit to all of u, please don't laugh at me :(
i am trying to start somthing here, i am selling on ebay, droppshiping from china, i have no idea what is going on with the tax, do i need to open ABN nomber? is it like a bussnis?
i just moove here to au, and i am alittle bit confused about the rules and everything...i know there is a subject about this issue here in this forum, but i can't find it, please if someone can tell me how do i find out about the tax for ebay?
i mean if i sell somthing do i need to pay the tax? i know there is everytime i am selling somthing - it's show 'get paid send invoice', i never send it, and i never received from any buyer on ebay....
anway i really need hellp, i hope i am doing the right thing. if not - what is the right thing to do?
thanks!!!!
reut

Lol you are not required to pay any tax at all. You only pay tax when you file a tax return. If you don't file a tax return, then their will be no tax at all.

but is it a legal,not to file a tax returne? i mean i am doing a profit so i need to pay tax-am i?

yes, highly illegal if you are running a business and don't declare income. I believe the ATO is planning a crackdown in ebay business as they have identified it as an area of great loss of tax. If you do it as a hobby then there is no tax payable. Best speak to an accountant to work it whether it is classed as a hobby or business

If you sell more than $75000 pa, then you need to declare it as a business and need a ABN.
Check out:
A New Tax System (Goods and Service Tax) Act 1999-section 13-20.

It's better to keep it legal, rather then trying to cheat.
You save yourself a lot of money in the long run, really.

Frank of Oz