If a borrower is declared bankrupt then in which head BAD DEBTS of the borrower would be showed at the end of the year in the books of borrower?

Funds would be written off the receivables in the lender's books. As per concept of prudence, following entry would be passed in the books of a lender:-

Dr. Bad-Debts expenses                                         xxx

Cr. Borrower (Receivable)                                             xxx