While both internal and external auditors evaluate public finances, they occupy completely different institutional spaces and serve distinct masters. An internal audit unit operates inside the government agency, functioning as a continuous managerial control tool. External audit (the SAI) operates entirely outside the executive branch, reporting directly to the legislature.

A strong internal audit function provides a critical line of defense. External auditors from the SAI evaluate the quality, independence, and working papers of the internal audit unit. If the internal audit team is highly capable, the external auditors can rely partly on their findings, allowing them to optimize their field testing and focus on higher-risk national issues.