Hi,
Capital gains tax liability arises where the disposal value of the shares is greater than the allowable costs (including purchase price).
To work out if there is a gain, all values must be in GBP Sterling.
To conver to Sterling, you need to use a just and reasonable exchange rate that would be in use at the time or acquistion or disposal.
Where the shares were a gift, you would need to use the market value of the shares when they were gifted to you or the market value of the share when received from the trust.
You are free to use any of the HMRC exchange rates at
Exchange rates from HMRC in CSV and XML format or you can obtain from a source of your choosing, such as the London stock exchange.
The disposal of the share should be declared in a self assesment tax return.
Thank you.