It really hinges on just how closely your idea of "dabbling" matches the ATO's.
Here is a reasonably good primer on the tax implications of trading CFDs. Be aware, however, that the comments in that article about CGT on CFDs are
inaccurate, as confirmed
here by the ATO (i.e.
CGT never applies to CFDs because no asset is ever acquired - it's a derivative contract).
And
here is the ATO's official position, with the relevant section extracted as follows:
Ruling:
11. A gain from a financial contract for differences will be assessable income under section 6-5 of the Income Tax Assessment Act 1997 (ITAA 1997) where the transaction is entered into as an ordinary incident of carrying on a business, or where the profit was obtained in a business operation or commercial transaction for the purpose of profit making.
12. A loss from a financial contract for differences will be an allowable deduction under section 8-1 of the ITAA 1997 where the transaction is entered into as an ordinary incident of carrying on a business or in a business operation or commercial transaction for the purpose of profit making.
13. A gain from a financial contract for differences will be assessable income under section 15-15 of the ITAA 1997 where a taxpayer enters into a financial contract for differences in carrying on or carrying out a profit-making undertaking or scheme, and the gain from it is not assessable under section 6-5 of the ITAA 1997.
14. A loss from a financial contract for differences where the gain would have been assessable under section 15-15 of the ITAA 1997 is an allowable deduction pursuant to section 25-40 of the ITAA 1997.
15. A gain or loss from a financial contract for differences entered into for the purpose of recreation by gambling will not be assessable income under section 6-5 or section 15-15 of the ITAA 1997 or deductible under section 8-1 or section 25-40 of the ITAA 1997. A capital gain or capital loss from a financial contract for differences entered into for the purpose of recreation by gambling will be disregarded under paragraph 118-37(1)(c) of the ITAA 1997.
A "dabbler" would need satisfy the ATO that they are only a recreational gambler (i.e. a very occasional trader, with very little expertise in the stock market, who doesn't approach the activity with a profit-making mindset) . I would venture to say that the average CDF punter would be considered to be approaching their CFD trading as a profit-making undertaking, no-mater how casual they might be, and thus dealt with under clauses 13 and 14, above (i.e. profits and losses are treated as assessable income - on income account, not capital (CGT) account).
BTW, to pre-empt any questions about CGT applying to CFDs, the answer is "no" because nowhere in that ATO ruling is there any reference to the CGT provisions applying.
