CGT Tax Rates and CGT Annual Exempt Amount for transactions before and after 30/10/2024

CGT Tax Rates for share disposals changed on 30/10/2024 for Basic Rate Tax Payers from 10% to 18%. If someone makes a £3000 gain before 30/10/2024 and another £3000 gain after 30/10/2024 in same tax year on selling shares - how much CGT do they pay? If £3000 annual allowance is taken from first transaction they pay £3000*18% on second transaction only, i.e. £540 or If £3000 annual allowance is taken from second transaction they pay £3000*10% on first transaction only, i.e. £300 Which is it or is it something else?

Hi,
You can choose which transaction you want to use the annual allowance against for the relevant rate of tax to be applied on any difference.
Thank you.