Gain/Loss on trading share options on US stock market

I'd like to inquire how I should report the following individual cases in the tax return: [Case 1] Assume I paid a premium of US$10,000 to buy Dec-22 Long Call share option on US stock market in Oct 2022. At the closing date of Dec 2022, the market price of the underlying share was above the option exercise price and I sold it at US$25,000. That meant I made a profit of US$15,000 in this trade. My questions are: 1. is this gain subject to Capital Gain Tax in nature? 2. is it correct to use Dec-22 & Oct-22 exchange rates in calculating the selling prices & premium paid respectively in order to obtain the gain in £? [Case 2 - please ignore Case 1] If the market price of the underlying share was below the exercise price, so I incurred a loss of US$10,000 in this trade. Is this loss allowable to carry forward for offsetting other capital gains of the future years? Thank you.

Hi Eunice Tang,
If you are resident in the UK, then yes the gain will be subject to UK Capital Gains Tax and should be declared in a Self  Assessment Tax return.
If the the opposite arises and a loss occurs.
This can be declared in a Self Assessment Tax return and the loss carrief forward for offsetting against other capital gains.
HMRC gives you several alternative exchange rates to use, besides the official closing exchange rate on the day of the transaction.
You are free to use any of them.
They can be found at:
.Exchange rates from HMRC in CSV and XML format
Thank you. 

 

In my case I sell a long put option and got a premium. At the closing date, the price of the stock was above the option exercise price, so the option didn't exercise. The gain of this case need to subject Capital Gain Tax ? Thank you.