According to IIA guidance, the chief audit executive (CAE) is directly responsible for establishing the objectives, scope, and plan for each engagement. This responsibility ensures that each audit is properly focused and aligned with the overall goals and risk areas of the organization. While maintaining a quality assurance program and providing professional development opportunities are important, they are not solely the CAE's responsibility without management support. Periodic review and approval of the internal audit charter is typically a joint responsibility with senior management and the board. Reference:
The IIA's International Standards for the Professional Practice of Internal Auditing (Standards), Standard 2010 - Planning.
The IIA's Practice Guide on Developing the Internal Audit Plan.