Bad debt refers to money that is owed by a debtor who is unlikely to pay it back. The most common causes of bad debt are death, bankruptcy or insolvency, and the inability to pay due to ill health. The term bad debt can also be used for loans that were made to someone who was never going to pay them back.In order for a debt to be considered a bad debt, the creditor must be able to prove that the debtor is going to default on the loan. For example, if a creditor is owed money by someone whose business has gone bankrupt, they can claim the debt as bad if they can prove they have lost money as a result of their business failure.