This may incur vigorish

• Borrower's note
• Debtor bettor's letters
• Slip in some pots
• Debt memo
• Piece of paper in a poker pot, perhaps
• Note in lieu of cash
• Letters written before a dollar amount, sometimes
• Written promise of a sort
• "Got you next time" letters

Wikipedia Word definitions in Wikipedia
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. ...