credit note 是『退款單』(不知中文有否官方翻譯？) 賣家多收了錢，把錢退回去，附加的單子就是 credit note.
debit note 是 『賬單』。賣家開給買家，催促繳款。
invoice 是debit note 的一種，列出交易明細。
credit note: A form or letter sent by a seller to a buyer, stating that a certain amount has been credited to the buyer's account.A credit note is issued in various situations to correct a mistake, such as when (1) an invoice amount is overstated, (2) correct discount rate is not applied, (3) goods spoil within guaranty period, or (4) they do not meet the buyer's specifications and are returned.
debit note: A form or letter issued by a seller to advise the amount owed by the buyer.
invoice: A detailed list of goods shipped or services rendered, with an account of all costs; an itemized bill.
2011-12-08 22:19:33 補充：
Oh, 所以『請款單』的英文是 debit note.