<p>The expanded audit report has been widely introduced in an effort to make audit reports more informative to investors in recent years. Prior studies indicate that the adoption of expanded audit reports is not significantly related to market reactions, generally measured by short-window abnormal returns and trading volumes, causing some to question the benefits of the new reporting regime. Unlike prior studies, we examine whether the adoption of expanded audit reports affects the stock price informativeness, measured by proxies using return data over a longer time period. Based on our difference-in-differences analysis results obtained from UK-listed firms, we find that the adoption of expanded audit reports causes a significant increase in informational efficiency and idiosyncratic volatility, and a significant reduction in crash risk. It means that, the expanded audit report improves the degree to which stock prices impound all available information and the extent to which firm-specific information is incorporated into stock prices. It also mitigates the incidence of subsequent stock price crashes. Our evidence indicates that the expanded audit reporting is informative to investors, but investors require time to assimilate information contained in expanded audit reports.</p>