台灣會計師公費揭露規範要求企業若符合非審計公費過高、更換事務所且審計 公費降低、或審計公費大幅降低者，應揭露會計師公費資訊，可知主管機關對 審計公費調降之疑慮甚於調升。本研究以2002年至2011年期間上市櫃公司為 研究對象，從公司治理觀點探討審計公費調降之決定因素。實證結果顯示，獨立董事比例及外國機構投資人持股率與審計公費調降間具顯著正相關，支持會計師供給面觀點。再者，四大事務所較能夠以服務品質異質化之策略，抵抗公司要求調降審計公費之壓力。會計師事務所在被首次委任查核時之審計公費調降可能性較高，隱含低球競價現象亦存在於審計公費變動之分析。最後，不論考量財務困難公司樣本、會計師自我選擇、核心代理問題之衡量方式、控制信用風險、會計風險、金融海嘯與極端值、會計師個人任期後，本文結果依然穩健。 Before 2009, the Taiwanese disclosure regulations with regard to audit fees required listed companies to disclose their auditor fees if they met any of the following criteria: (1) pay abnormally high nonaudit fees to their auditors; (2) change their audit firms along with a decrease in audit fees; (3) firms’ audit fees decrease dramatically. This implies that regulators in Taiwan were more concerned with decreases in audit fees than increases. This study uses listed companies during the period 2002 to 2011 to explore the determinants of audit fee decreases from the perspective of corporate governance in Taiwan. First, the empirical results are consistent with the supply-side perspective, which claims that both the proportion of independent directors on the board and the degree of foreign institutional ownership are significantly and positively associated with the probability of audit fees decreasing. Moreover, Big 4 audit firms are more likely to use the audit-quality differentiation strategy to resist pressure from their clients who want lower audit fees. The probability of reducing audit fees is higher when the company changes audit firm, implying that the practice of low-balling occurs in this context. Finally, the empirical results are robust after taking into account the sample of financially distressed companies, self-selection of auditors, the measurement of core agency problems, credit risk, accounting risk, global financial crisis, outliers, and partner-level tenure.