If anyone is trading shares without understanding the tax...

If anyone is trading shares without understanding the tax implications, then I suggest they read up and/or consult someone with knowledge IMMEDIATELY. It is remarkably simple and can be summed up in two steps (for a majority of assets owners)
1. You need to hold a share for one year or more to receive a 50% capital gains tax discount
2. Your capital gains can be offset by capital losses (hence why people often sell near the end of the financial year), with the net figure taxed at your marginal tax rate less any discounts.

If you don't understand these two aspects of share ownership, then you place yourself at risk of a nasty tax fright!