Substantive analytical procedures, when effective and the results are satisfactory, can, in most audit systems, enable the auditor to significantly reduce the amount of detailed substantive audit testing. They can often provide evidence for multiple assertions and may even identify issues that may not be obvious from more detailed audit work, such as highlighting deficiencies in internal controls. They can be particularly useful in circumstances in which tests of transactions cannot provide adequate evidence of completeness and can be particularly effective when combined with testing the operational effectiveness of controls.