an option question

Sorry this is off topic to the recent excitement but I have had this question in my mind for a while..
Might be a silly one but I can't find the answer and would appreciate if a more knowledgeable poster might answer for me...

I have traded options quite a few times but have never actually exercised them... I feel that this might be a company that I may be doing that in the future and my question is this...
Is it a CGT event on the profit that you have made on the options when you exercise the options or when you eventually sell the shares ?

eg, if I bought 10,000 options at 1c then they go to 10c so I have 900 bucks profit .. then I exersise them into ordinary shares...do I still have to pay the tax on the 900 bucks?

Tx in advance and GL to all here.