According to IIA guidance, internal auditors should use relevant information obtained during a consulting engagement to inform and enhance their evaluation of internal controls during related audit engagements. This is because the knowledge gained from consulting activities can provide valuable insights into the functioning of controls and processes, which can be applied when assessing their effectiveness in a subsequent audit.
IIA Reference:
IIA Standard 1220: Due Professional Care indicates that internal auditors should consider all relevant information available to them when making judgments and recommendations. This includes information obtained from consulting engagements.
The IIA's Practice Guide on Consulting Engagements advises that while internal auditors must maintain objectivity, they can and should use knowledge gained from consulting engagements to enhance the value and accuracy of their assurance work.