IOU

An IOU is an informal document that acknowledges a debt owed. IOU is an abbreviation, in phonetic terms, of "I owe you." The debt owed does not necessarily involve a monetary value but can also involve other products. With IOUs being informal, those issuing the IOU are given free reign when writing and issuing an IOU. Things like time, date, interest, and payment type are not mandatory but may be implied.