本研究的目的在於比較集團與非集團企業的避稅程度，並檢視外部機構投資人的存在是否可降低企業的避稅行為。實證結果顯示，在其他條件不變下，相較於非集團企業而言，集團企業的避稅程度較高，隱含相較於避稅可能引發的潛在稅務風險而言，台灣的集團企業反而較著重於避稅所帶來的利益。此外，實證結果亦顯示負債比率較低、獲利能力較高及從事較多關係人交易的企業會有較高的避稅傾向。然而，針對機構投資人對企業避稅行為的影響上，本文並未觀察到機構投資人持股對企業而言有任何的外部監督效果。

This study aims to compare the level of tax aggressiveness between group and non-group enterprises, and to examine whether the presence of institutional investors would reduce the tax avoidance activities. The empirical results show that compared to non-group firms, group firms are more tax aggressive, ceteris paribus. This result implies that Taiwanese group firms are more concerned with the benefit from tax savings than the potential penalty imposed by the tax authorities. And the results show that the enterprises will be more tax aggressive when they have lower debt ratios, better profitability, and larger related party transactions. However, this study doesn’t find that institutional investors have the outside monitoring effect on tax aggressiveness of group and non-group firms.