CGT - shares

Hi Can you help pls? I bought some Debenhams shares on the stock market in June 2018, in May 2021 Debenhams went into administration and I lost my money, I have no connections to the company. I have completed my 23/24 self assessment and had already paid CGT on another investment in this ax year, could I have declared the Debenhams loss on my self assessment and if not, can I? Is there anywhere I can still declare? Many thanks for your help.

Hi, yes, this would be a  negligible value claim - Negligible value claims and agreements
Thank you.