Can someone give me a definition of "key internal control" as opposed to just an internal control?

Answer 1

Internal control is the process designed, implemented and maintained by those charged with governance, management and other personnel to provide reasonable assurance about the achievement of an entity’s objectives with regard to reliability of financial reporting, effectiveness and efficiency of operations, and compliance with applicable laws and regulations. The term “controls” refers to any aspects of one or more of the components of internal control.

Key Internal Controls are those controls designed to meet the company's control objectives and address management’s financial statement assertions for MATERIAL activity. Management relies upon these controls to prevent and detect MATERIAL errors and misstatements.

ISA 315.12 says, "The auditor shall obtain an understanding of internal control relevant to the audit. Although most controls relevant to the audit are likely to relate to financial reporting, not all controls that relate to financial reporting are relevant to the audit. It is a matter of the auditor’s professional judgment whether a control, individually or in combination with others, is relevant to the audit."

The auditor does not test every control in existence, only those controls the absence of which can lead to MATERIAL misstatement of the financial statements.