Promissory /(?)/

Prom·is·so·ry

Promissory

a.
  1. Containing a promise or binding declaration of something to be done or forborne.

Phrases & Compounds
Promissory note
a written promise to pay to some person named, and at a time specified therein, or on demand, or at sight, a certain sum of money, absolutely and at all events; -- frequently called a note of hand.