A debit note or debit memorandum (memo) is a commercial document issued by a buyer to a seller as a means of formally requesting a credit note. A seller might also issue a debit note instead of an invoice in order to adjust upwards the amount of an invoice already issued (as if the invoice is recorded in wrong value). Debit notes are generally used in business-to-business transactions. Such transactions often involve an extension of credit, meaning that a vendor would send a shipment of goods to a company before the goods have been paid for. Although real goods are changing hands, until an actual invoice is issued, real money is not. Rather, debits and credits are being logged in an accounting system to keep track of inventories shipped and payments owed.