Simply put, it is to improve efficiency. Theoretically, the audit purpose can be achieved without relying on internal control and only relying on substantive testing, but the cost will be unbearable.

The better the internal control of an enterprise, the fewer substantive procedures will be implemented, but it cannot be ignored just because the internal control is good.

On the contrary, the worse the internal control, the more we check one by one, but it is meaningless to collude with fraud by internal control.