A negotiable instrument must include an order to pay or a ______.

A negotiable instrument must include an order to pay or a promise to pay to be valid and enforceable. This means that the document must clearly express the intent to pay a specific amount of money either on-demand or at a specified future date, creating a legal obligation for the payer.

In the context of negotiable instruments, the promise to pay establishes a clear commitment from the issuer, such as in a promissory note, ensuring that the holder has a right to receive the designated funds. This characteristic is essential because it provides certainty and security for all parties involved in the transaction.

While a flexible sum of money may refer to the variability of payment amounts, a handwritten signature may serve as a form of authentication, and a notary stamp is primarily used for verifying the identity of signers and the legitimacy of documents, these elements do not fulfill the fundamental requirement for a negotiable instrument. The requirement for a clear order or promise to pay is what fundamentally defines the instrument's negotiability.