According to PSA 330, how often should an auditor test unchanged controls?

PSA 330, which focuses on the auditor's responses to assessed risks, stipulates that an auditor should test unchanged controls on a periodic basis to ensure they continue to operate effectively. Testing these controls every third audit allows the auditor to maintain a balance between efficiency and the adequate assessment of controls' effectiveness.

This timeframe is grounded in the understanding that while some controls may remain effective over time, periodic testing is necessary to confirm their operational integrity and to address any potential changes in the environment or processes that may affect their performance. Consistent re-evaluation helps auditors gather sufficient evidence about the reliability of these controls, ultimately contributing to the audit's overall effectiveness and the assurance provided to stakeholders.

The other options do not align with the guidance provided by PSA 330. Testing controls after every two audits or at every additional audit could lead to overlapping testing efforts or unnecessary resource allocation, while only testing upon request from management would not ensure a systematic approach to risk assessment and may overlook the importance of auditor independence and responsibility in evaluating internal controls.