Concept:A debit note is sent by a buyer to a supplier when goods are returned because they are unsatisfactory.Explanation:The buyer returns unsatisfactory goods to the supplier.The buyer sends a debit note to inform the supplier that the supplier's account has been debited.This means the supplier now owes the buyer for the value of those returned goods.Therefore, the correct document is a debit note, not a credit note, invoice, or waybill.Answer:Debit note