I guess it would depend on the tax laws in your country. Here in Australia that is not true.
If the tax office classes you as a trader you will pay tax on any money earned through trading whether you have withdrawn it or not. However, if the tax office doesn't deem you a trader your trading activities are classed as gambling and here in Australia you do not pay tax on any winnings and can not claim any losses against other earnings.
It seems the definition of trader versus gambler is whether you are consistantly making money. As soon as you are consistantly profitable the tax office likes to class you as a trader for obvious reasons!
Cheers,
PKFFW
