The document outlines the audit frequency norms for service tax assessees as per guidelines from the Director General of Audit, New Delhi. Mandatory audits are required annually for taxpayers with service tax payments of Rs. 3 crore or more, while other taxpayers are audited based on various thresholds and intervals. The document also emphasizes risk assessment in selecting non-mandatory taxpayers for audits, along with guidelines to avoid duplicative audits and scrutinizations.