PurposeThis study examines (1) the extent of key audit matters (KAMs) reported by auditors is related to accounting estimates, (2) whether measurement uncertainty and management bias affect auditors to do so and (3) whether the use of accounting estimates, given the measurement uncertainty and management bias reported in KAMs adversely affects the decision usefulness of accounting information.Design/methodology/approachData on key audit matters, accounting estimates, measurement uncertainty, management bias, etc. were collected from the auditor's reports of 351 sample Chinese listed firms. It employs regression analyses to assess the hypotheses on issues affecting the report of these key audit matters and the impacts on the decision usefulness of accounting information.FindingsFair value and impairment loss estimations make up of 2.6 and 44.1% of the 606 KAMs identified, respectively. Measurement uncertainty is positively, while management bias is negatively, affecting auditors report KAMs related to accounting estimates. The use of accounting estimates in firms where their auditors reported the KAMs related to accounting estimates does not enhance the value and predictive relevance of reported earnings. The assurance works on, and reporting of, KAMs served as a “red flag” about the accounting estimates.Practical implicationsThe use of accounting estimates does not always lead to enhanced decision-useful accounting information. Auditors, in their stewardship role, shall ensure that the measurement uncertainty issue is appropriately identified, addressed and verified. In addition, they shall provide an effective check-and-balance to the accounting discretion managers have in providing decision-useful information from opportunistic reporting.Originality/valueThis study examines the proposition that while the use of estimates can enhance the decision usefulness of accounting information, it can also induce measurement uncertainty and management bias into financial reporting.