Dishonour of negotiable instruments: refusal to accept or pay upon due presentment defines instrument dishonour under presentment rules. Dishonour denotes refusal to accept or pay a negotiable instrument when duly presented; it occurs where a necessary or optional presentment is made and due acceptance or payment is refused, cannot be obtained within the prescribed time, or, in bank collections, the instrument is seasonably returned by the midnight deadline; presentment excused but absence of due acceptance or payment also constitutes dishonour.