Loan carrying value is the amount of the loan per your accounting books. Assume you had a $200,000 loan on the books. It is deemed to be impaired and $20,000 is written off. Now the books show a $200,000 debit in the loan acct and a $20,000 credit balance in a Contra Loan acct "Impairments". So there is a net $180,000 on the books and that is also the carrying value of the loan.