18yr old stealing

[biffandchip]

DS18, youngest of 3 boys. Lovely kid but always had a sense of entitlement. Took things that were for his brothers eg clothes, sweets, food and stole money from them. Progressed to stealing money from my purse. I now use a coin purse and only have a debit card as he takes any money I have. If I do have money I sleep
with my purse. He has a part time job in a specialist sports role and is very well paid. He has more monthly disposable income than I have. When at work I noticed my debit card was not in my purse. I cancelled the card immediately and checked my balance. 4 transactions that could only have been made by him. I come home from work, don’t say anything, only for card to reappear in my purse within minutes. When confronted DS denies everything. Not him, he hasn’t used it etc. borderline gaslighting me. I have told him he has committed a criminal act etc. he doesn’t care and I think he convinces himself he hasn’t done anything. What on earth can I do. I really don’t know how to move forward. His brothers have never stolen anything, everything in the family seems to be fair game for him.