Tax refund 23000£ plus uc

Hi please tell me what to do i receive 23000 from tax refund for 3 vears a go from my company and iam or universal credit from two months ago and I take advance payment from universal credit put the tex refund money go to the company card and I don't tell the uc i have company and I haven't give them the company details What do vou recommend me to do to stop the uc or to tell them