Which role must determine the effectiveness of design controls in an internal control system?

The role that must determine the effectiveness of design controls in an internal control system is primarily that of management. This is because management is responsible for establishing, maintaining, and assessing the effectiveness of internal controls across the organization. They must ensure that the controls are designed appropriately and functioning as intended to achieve the organization’s operational and compliance objectives.

Management's responsibilities include conducting risk assessments, implementing internal controls to mitigate those risks, and continuously monitoring the system to ensure it remains effective. They are in the best position to evaluate how well these controls function in practice since they have direct oversight of daily operations and decision-making processes.

While other roles, such as internal auditors, support the evaluation process by providing an independent assessment of the internal controls, the ultimate responsibility for determining their effectiveness lies with management. Thus, they play a crucial role in fostering a culture of accountability and compliance within the organization.