Ferrari308 the reason the date is date of conversion for capital...

Ferrari308 the reason the date is date of conversion for capital gains tax is when you acquire options you have not entered into a contract to buy the shares, as you are not under any obligation to buy them. You have merely bought a right to require the option writer to sell you an asset at a future date for a fixed price (at least in the case of company share options).

The payment made for the options is technically not part of the purchase price of the shares (although for capital gains tax purposes it is included). It is payment for the writer's commitment to sell the asset to you at a future date (or in the case of options bought on market the payment is for the seller effectively assigning you the entitlement to require the option writer to sell you the asset).