bad debt 
noun
A debt that cannot be recovered.The financier eventually receives the proceeds of the debts, the trader usually agreeing to repurchase any bad debts....
- As the accounts stated, the loss was due to claims under a policy written for the solicitors' indemnity fund and for bad debts on reinsurance recoveries.
- The financial crisis has now left many of these banks on the verge of insolvency with large portfolios of insecure loans and bad debts.