Iowa Code § 490.807: Resignation of directors.

1. A director may resign at any time by delivering a written notice of resignation to the board of directors or its chair, or to the secretary.

2. A resignation is effective as provided in section 490.141, subsection 9, unless the resignation provides for a delayed effectiveness, including effectiveness determined upon a future event or events. A resignation that is conditioned upon failing to receive a specified vote for election as a director may provide that it is irrevocable.