Professional audit firms increasingly engage in Corporate Social Responsibility (CSR) activities. This paper examines the effect of audit firms' CSR activities on auditors’ reputation. We find that audit firms that engage in CSR experience an increase in the size of their client base compared to audit firms that do not engage in CSR. The effect is stronger for audit firms without existing reputation from a Big 4 brand name or industry specialization. We also find that clients that value CSR are more likely to hire audit firms that engage in CSR. Overall, our results suggest that CSR is an effective tool for audit firms to build their reputation in the marketplace.

We examine the adoption of expanded audit reports that include key audit matters (KAMs) in Hong Kong (2016) and mainland China (2017). These jurisdictions are highly integrated and together constitute one of the largest economies to adopt the IAASB's reporting standards in a staggered fashion, while also differing in investor protection and legal enforcement. Using matched samples, pre‐post tests, and staggered difference‐in‐differences analyses with company fixed effects, we do not find compelling evidence that expanded audit reports affect market reactions or audit quality. These findings suggest a substantial gap between regulatory intent and implementation—on average, in these markets, KAMs do not appear to meet investors' demand for incremental information or to improve audit quality substantially. At the same time, our cross‐sectional evidence on KAM characteristics is more nuanced. A higher number of KAMs and the presence of novel or transaction‐specific KAMs are associated with stronger pricing of fundamentals, consistent with investors perceiving the related financial statements as better vetted. Yet a higher number of KAMs and novel KAMs are also associated with lower profitability persistence, consistent with these disclosures reflecting company risk and volatility. In contrast, industry‐common KAMs appear less relevant for valuation, consistent with investors discounting routine disclosures, even though they are associated with more persistent performance likely reflecting more stable industry conditions. Overall, our evidence suggests that mandating expanded audit reports alone may be of limited value, whereas better tailored KAM disclosures may still serve as signals of firm fundamentals and future performance.