DEVELOPING A STRUCTURED DUE DILIGENCE METHODOLOGY FOR AUDIT FIRMS: A RISK-BASED PERSPECTIVE

The expansion of audit-related services has increased the need for audit firms to provide due diligence engagements that are systematic, risk-sensitive, well documented and compatible with professional quality management requirements. In practice, due diligence is often performed through fragmented checklists or expert judgment, which may create inconsistency in risk identification, evidence collection, reporting and engagement quality. This article develops a structured due diligence methodology for audit firms from a risk-based perspective. The study applies qualitative document analysis, comparative standard mapping and design-science logic to synthesize requirements and principles from ISRS 4400 (Revised), ISAE 3000 (Revised), ISQM 1, OECD risk-based due diligence guidance, ISO 31000 risk-management logic and contemporary sustainability due diligence developments. The proposed methodology consists of seven interconnected stages: engagement acceptance, scope and criteria definition, risk-universe construction, targeted evidence planning, analytical testing, risk scoring and decision-oriented reporting. The results present a practical framework, risk matrix, quality gates, working paper structure and reporting architecture that audit firms can adapt for financial, tax, legal, operational, governance and ESG due diligence. The article argues that due diligence should not be treated merely as a transaction checklist but as a disciplined professional service governed by risk assessment, ethical safeguards, documentation standards and firm-level quality management. The proposed model strengthens comparability, transparency and usefulness of due diligence reports for investors, owners, lenders and other decision-makers.