Vested but not exercised RSU

Hello! I moved to the UK a year ago. During my previous employment I was awarded with RSU of non-UK company listed in the US for the work outside of the UK. The vesting date of the RSU is before arrival to the UK. The employer hasn't payed any taxes in accordance to the tax laws in the country of residence. The trade of the company was halted on the market and thus I was not able to exercise or sell RSU before moving to the UK. My question is, once I am able to exercise (and receive shares) or exercise-and-sell my RSU, what taxes should I pay in the UK? How do I fill my set assessment form?

Hi fixity,
HMRC cannot comment on future events as legislation and/or plans may change.
Based on current guidance, you may be liable to Capital Gains Tax when you sell them.
Thank you. 

Thank you for the response! In order to correctly calculate capital gains tax, what price should I use to estimate initial value of the assets? Should I use the price at vesting date? If selling price less then the initial price, can I report capital gain loss?

Hi,

Please see guidance at:

ERSM180020 - CGT Interface

Thank you.