A credit note or credit memorandum (memo) is a commercial document issued by a seller to a buyer. The seller usually issues a credit memo for the same or lower amount than the invoice, and then repays the money to the buyer or sets it off against a balance due from other transactions.
It can also be a document from a bank to a depositor to indicate the depositor's balance is being in event other than a deposit, such as the collection by the bank of the depositor's note receivable.