A written promise whereby the maker (issuer, payor, obligor, or promisor) unconditionally commits himself to pay or repay another person or the bearer (payee, obligee, or promisee) a stated amount of money either on demand or at a determined or determinable future date, with or without interest. A promissory note is not just an IOU, but it also involves an undertaking (promise) to pay. Promissory notes can be negotiable; that is, they may be sold for cash, usually at a slight discount from the full value (borrowed amount plus interest). Bearer notes are based on a promise by the borrower to pay the bearer the amount owing. In many countries today, bearer negotiable promissory notes are forbidden by law, lest people use them as an alternative currency.

Promissory notes come in different flavors including: lump sum notes, installment notes (amortization notes), and demand promissory notes.

It is often called a note of hand or, simply, a note.