本文以台灣上市公司為研究標的，針對研究期間為 1997 年至 2012 年間公司曾發生過購併事件者，探討對會計師簽發審計意見類型之影響，藉以了解會計師簽證保守性。實證結果發現(1)公司於年度購併與公司財務報表遭會計師簽發非無保留之審計意見呈現顯著之正向相關，顯示因購併使審計風險與訴訟風險增加而導致會計師以更保守之態度執行查核，表示公司購併會影響會計師簽證保守性。(2)公司購併型態為純水平式與年度財務報表遭會計師簽發非無保留之審計意見呈現顯著之負向相關；(3)公司購併型態為純垂直式與年度財務報表遭會計師簽發非無保留之審計意見呈現顯著之正向相關，表示企業購併對審計決策的影響程度，會隨著購併型態之所屬產業差異程度而有所影響，而購併型態之產業垂直相關程度對審計意見決策的影響上具有加乘效果。
換言之，購併受到跨越產業別之關係而會計師因對各產業瞭解程度有別而使審計決策愈趨於穩健保守，當公司為純水平式購併，會計師因為對相同產業瞭解程度愈高因而愈不會簽發非無保留意見查核報告；而當公司為純垂直式購併，會計師將以更保守之態度執行查核而愈不會對其簽發無保留意見。綜合以上結論，企業購併使審計風險提高，將導致會計師以更保守之態度執行查核，並隨著購併型態而有不同影響程度。

Mergers and acquisitions (M&As) have been an active economic activity since the 1980s. They have played an important role in economic growth and increase market power. Such activities arouse stakeholders’ concerns including the disclosure of financial information and the type of audit report issued by auditors. This paper aims to investigate Taiwan domestic individual firms’ audit reports after their M&A activities and comparing them with non-participants. We evaluate whether M&A activities reduce the likelihood of firms receiving auditor unqualified opinions, since business failure and audit failure followed by negative news are likely to attract regulators’ scrutiny and investor class-action lawsuits. Prior studies indicate that legal liability and litigation risk affect auditors’ decisions. Therefore, we predict that, to reduce the risk of litigation, auditors will less likely to issue unqualified opinions after M&A activities involving their clients.
We evaluate this prediction empirically and find that the probability of issuing without unqualified opinion is positively associated with the occurrence of M&As. Further analysis indicates that this positive relation is also significant for firms with pure vertical merger patterns but negatively associated with firms with pure horizontal merger patterns. Our findings show that M&A participants are less likely to receive unqualified opinion, indicating that audit risk and litigation risk affect auditor conservatism.

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