How to calculate capital gains tax for free shares

I was awarded for free some shares of a bank as a welcoming gift when I opened a bank account with them. I understand that the free shares is subject to capital gains tax (CGT). My questions are: (1) When should I report the awarded free shares to HMRC? In the tax year that the shares is awarded or in the tax year that the shares is sold? (2) How to calculate the CGT? Should the cost be GBP 0 such that the total value of the shares sold is subject to CGT? Thank you very much.

Hi,
You would only report them if you sell them.
Yes you purchase price will be 0
Thank you.