IOU

An IOU (abbreviated from the phrase "I owe you"[1][2]) is usually an informal document acknowledging debt.

IOUs may be signed or carry distinguishing marks or designs to ensure authenticity.

In some cases, IOUs may be redeemable for a specific product or service rather than a quantity of currency, constituting a form of scrip.

[3] Also referred to as "IOUs" by the U.S. state of California, the term "Registered Warrants", which specify a future payment date, is meant to differentiate these IOUs from regular, or “normal” payroll warrants which permit the holder to exchange their warrant for cash immediately.

[4] Warrants are issued as payment to state employees, private businesses, local governments, taxpayers receiving tax refunds, and owners of unclaimed money.