IOU

What Does IOU Mean?
An abbreviation of the phrase "I owe you." 

Investopedia explains IOU
An IOU in the business community is actually a legally binding agreement between a borrower and a lender. The terms of the loan are set out in a contract, and, once it's signed, the two parties must abide by the terms of the contract or face legal repercussions. For example, when a corporation issues bonds, it is in essence issuing an IOU to bondholders. The IOU or bond contract sets out the terms, including the principal that will be owed, the interest that will be paid, and the time at which these payments will occur.