Using the earnings response coefficient (ERC) from a returns-earnings model, this study examines the impact of the Standard Audit Hours Policy (hereafter, SAHP), introduced in 2019, on the informativeness of earnings for companies listed in the Korean stock markets over the period from 2017 to 2020. We further explore whether earnings informativeness is enhanced by increases in audit hours and audit fees following the adoption of the SAHP. First, our analysis does not reveal any consistently significant evidence suggesting that the adoption of the SAHP has enhanced the overall informativeness of earnings. Second, our analysis shows that firms with audit hours exceeding the year-industry average, as well as those with increased per-hour audit fees, do not demonstrate a significant improvement in earnings informativeness. This result holds true regardless of auditor size and persists across periods before and after the implementation of the SAHP. Third, our findings indicate that firms paying audit fees above the year-industry average achieve significantly greater earnings informativeness, especially when engaging non-Big 4 auditors and during the period following the adoption of the SAHP. Overall, the results of this study suggest that the effects of the SAHP on earnings informativeness differ by auditor size. Specifically, the post-SAHP increase in audit fees enhances the performance of smaller audit firms, leading to more favorable market responses to earnings information audited by these audit firms.