from wiki
An IOU is a usually informal document acknowledging debt. The term is derived from the opening phrase "I owe unto" and/or the pronunciation of "I owe you".
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IOUs from California are on their way
San Jose Mercury News
SACRAMENTO - With its bank balance careening toward zero, California began sending tens of thousands of IOUs to its creditors Thursday, the latest black eye for the state and its broken budget system.
Nearly 30,000 IOUs began rolling off state printing presses hours after officials agreed to pay recipients 3.75 percent interest on the notes. California will continue to pay about $3.4 billion of its obligations this month with scrip instead of cash if the governor and legislators don't soon find a way to balance the state's books.
It will be the first time since 1992 that vendors, taxpayers and social service providers will receive IOUs, formally known as registered warrants, from the state. The IOUs will mature Oct. 2 unless banks agree to honor them sooner.