Yes you should speak to your accountant.On the scenario you...

Yes you should speak to your accountant.

On the scenario you suggest you start with $10 you invest the $10 twice each time making $5 profit you now have $20 so you will be taxed on the total profit of $10.

The rate of tax will be determined by your marginal tax rate and whether you are entitled to claim the 50 % capital gains tax concession because during the time between buying and selling a period of 12 months or more has elapsed.

In speaking to your accountant you may wish to discuss whether there may be sense in having a a non earning dependent spouse buying and selling such shares as they would potentially have available the full tax free concession which was in the order of $22,000 per annum.

If you intend to seriously involve yourself in share trading the speaking to your accountant before you start is a must.

My opinion only DYOR.