Русско-англо-русский юридический словарь

An IOU (abbreviated from the phrase "I owe you") is usually an informal document acknowledging debt. An IOU differs from a promissory note in that an IOU is not a negotiable instrument and does not specify repayment terms such as the time of repayment. IOUs usually specify the debtor, the amount owed, and sometimes the creditor. (Wikipedia)