The IS auditor's first course of action should be to verify the results of the critical automatic calculations made by the system to determine the validity of user concerns. This is because the IS auditor needs to obtain sufficient and appropriate audit evidence to support the audit findings and conclusions. By verifying the results, the IS auditor can assess whether there are any errors or discrepancies in the system's calculations that could affect the accuracy and reliability of the financial data. The IS auditor can use various techniques to verify the results, such as re-performing the calculations, comparing them with expected values, or tracing them to source documents.