A written instrument which is signed by its maker (the drawer) and contains an unconditional promise or order to pay a particular amount of money, with or without interest, on demand or at a preset future time, to a specified person, or to the order of a named person, or to its bearer. A negotiable instrument must be signed by the maker, or his authorized agent if the instrument is a note or a certificate of deposit, or by the drawer, or his authorized agent, if the instrument is a check or a draft. Furthermore, it must contain (in except of a certificate of deposit) an express order or promise to pay, as merely acknowledging a debt is not sufficient without an affirmative pledge on the part of the debtor to repay the debt. A promise or order to pay is not negotiable if the instrument states an express condition to payment or that the promise or order is subject to another writing, or that the rights or obligations related to the promise or order are stated in another writing.

The main types of negotiable instruments include: drafts (time drafts, sight drafts, trade acceptance), promissory notes, certificates of deposit, and checks.

In terms of negotiability, negotiable instruments can be divided into order instruments and bearer instruments.