A bank note is not a source document. An invoice is a source document that is used to record a sale, a credit note is used to record a return of goods, and a debit note is used to record a deduction from a purchase. However, a bank note is a form of currency issued by a bank that represents a promise to pay a specific amount of money to the bearer upon demand. It is not a document that provides information about a business transaction and is not used in accounting as a source document.