ANS If you read the example of molly the Engineer in the ATO...

ANS If you read the example of molly the Engineer in the ATO link above, no reference to her obtaining an ABN is made.

You need to contact the ATO to find out whether your trading frequency is sufficient to be considered a trader ...... and if you are ..... run to a tax accountant who knows .......... because you may need to keep separate trading and investment accounts for an optimal tax outcome.

cheers