If you are a regular seller on ebay, you need to consider whether you are operating a business or whether you are selling as a hobby. In order to make this decision, you may need to get some advice from either a qualified accountant, or by ringing the Australian Taxation Office. There are many different elements to the operation of a business, but you may still be recognised as carrying on the conduct of a hobby. It is well worth your while seeking advice in this area, especially if you are making a regular profit which significantly increases your own personal living style. You also want to avoid being prosecuted for not declaring all of your taxable income. Under-reporting of taxable income can have serious consequences with not only the Taxation Office, but also with other government agencies such as Centrelink and the Child Support Agency.
If advice you receive indicates that you are operating a business, you will need to apply for an ABN (Australian Business Number) from the Australian Taxation Office. This can be done online. Once you have gone through the application checklist, you will receive your ABN online immediately. A hardcopy will be sent to you in the mail for your safekeeping.
If you have over $50,000 turnover from your ebay business, you will need to also register for GST. This means that all of your sales will be inclusive of GST which will need to be reported on a Business Activity Statement, and it also means that you can claim the GST which you pay on expenses associated with your ebay business. It is also worth while getting advice from a qualified accountant, or asking the Taxation Office for an advisory visit regarding GST and how to report it.
The best advice in this regard is to seek advice. If you cannot afford the services of an accountant, or would prefer not to, the Australian Taxation Office can answer most of your questions over the telephone. If you would prefer a field officer to visit you at home to go through your reporting obligations, this can be arranged easily also.