本文探討民國87年實施合一主要的兩項制度變革，股東可扣抵稅額及未分配盈餘加徵10%所得稅對上市公司融資決策之影響。兩稅合一制實施後，由於股東可扣抵稅額，將降低股利所得重複課稅，因而降低了公司為股東舉債節稅的利益。但未分配盈餘加徵10%所得稅，將使得舉債利息費用的責稅利益增加，反而提高公司舉債之誘因。本文的實證結果也發，其他情況不變下，在此新稅制下，上市公司稅額扣抵比率愈高者，其負債權益比率愈低；而未分配盈餘比率愈高者，其負債權益比率愈高。政府未來應評估現行對未分配盈餘加徵所得稅的政策，對企業融資經營的負面影響。

Enacted in 1998, the Integrated Income Tax System has two important features, i.e., the imputation tax credit (ICT) to shareholders and the 10% surtax levied on undistributed earnings. This study examines the impacts of the two important features on corporate financing decisions. After implementation of the Integrated Income Tax System, the imputation tax credits can reduce the double taxation on stockholders’ dividend income and, hence, reduce corporations’ debt-to-equity ratios. However, the 10% surtax on undistributed earnings may result in opposite effect on corporate debt-to-equity ratios. The empirical results of this study show that, certeris paribus, under the new tax system, companies with grater ITC ratios tend to have lower debt-to-equity ratios, while companies with grater undistributed earnings ratios tend to have higher debt-to-equity ratios, consistent with our expectations. The findings of this study have important implications for the government to take into account the potential adverse impacts resulted from taxes levied on corporations’ undistributed earnings.