本研究旨在探討我國實施兩稅合一制度後，稅額扣抵比率及未分配保留盈餘加徵10%營利事業所得稅在上市公司不同產業間的實行狀況，以及新稅制對上市公司資本結構及資金成本的影響，並評估這些結果是否有達成政府實施兩稅合一政策的主要目的，改善企業的資本結構及創造有利於企業的投資環境。本研究的研究範圍以兩稅合一實施前後，自民國85年至88年共四年度在台灣證券交易所之股票上市公司為研究樣本。 本研究結果顯示，在稅額扣抵比率方面，由於電子業上市公司相對於非電子業上市公司享有較多的租稅優惠，故其稅額扣抵比率顯著地低於非電子業上市公司。此外，在未分配盈餘加徵10%營利事業所得稅方面，民國88年度，我國被加徵未分配盈餘稅的上市公司中，大約有15%的公司民國87年度並無財務所得，但依所得稅法第六十六條之九計算的未分配盈餘卻為正值，顯見現行以課稅所得為基礎計算的未分配盈餘與財務會計的處理結果有很大的差異。至於未分配盈餘加徵的稅額，我國電子業上市公司即約佔38%，且其加徵稅的平均值也遠高於全部樣本之平均值。 在兩稅合一實施前，舉債較高且租稅負擔較低的公司，兩稅合一實施後，因新稅制減少了企業對於融資決策的扭曲，故有助於財務風險較高的公司改善資本結構。此外，公司的稅額扣抵比率愈高，則其舉債比率愈低。再者，在兩稅合一實施前，舉債較少且租稅負擔較高的公司，兩稅合一實施後，資金成本的變動呈現上升趨勢，與本研究預期相反，但本文實證結果仍發現公司的稅額扣抵比率愈高，則其資金成本愈低。因此，兩稅合一對於企業資金成本的降低仍具有效益。

本研究主要在探討近年來兩大租稅改革：兩稅合一制及最低稅負制之施行對上市公司外資持股比率之影響，是否降低外資持有我國上市公司股票之意願，影響我國企業的股權結構。 兩稅合一制施行後，消除股利所得之重複課稅，國內法人股東與自然人實質稅負減輕；但根據所得稅法第七十三條之二規定，非中華民國境內居住之個人、在中華民國境內無固定營業場所及營業代理人之營利事業，其獲配股利所含之稅額，不得扣抵其應納稅額，外資無法享受股東可扣抵稅額消除重複課稅的好處，外資在台投資實質總稅負仍維持為40%，較境內自然人股東之實質稅率6%~40%為高，股東可扣抵稅額比例愈高，外資損失越大。再者，最低稅負制施行主要影響對象為外資持股最多的電子業，且最低稅負制之施行對於公司補繳之稅負，外資股東也無法享受股利抵稅權。故可推論兩稅合一制、最低稅負制之施行及股東可扣抵稅額與上市公司外資持股比率應呈負向關係。 本研究之樣本為民國85年到民國95年及最低稅負制前、後之台灣上市公司。主要實證結果彙整如下： 1、兩稅合一制之施行及股東可扣抵稅額與上市公司外資持股比率呈負向關係，最低稅負制之施行與上市公司外資持股比率呈正向關係，但其效果應為股價指數之影響所致而非最低稅負制之施行；又最低稅負制施行後，外資仍偏好持有公司有效稅率低於10%之股票。 2、另外以民國93年到民國95年資料額外檢測，最低稅負制下限制投資抵減金額之效用，推論投資抵減金額在最低稅負制施行後與上市公司外資持股比率應呈負向關係，實證結果為負向關係但不顯著。 / The objective of this study is to examine whether the implementation of the Imputation Tax System and Alternative Minimum Tax System will affect the willing of foreign investors to invest in listed companies. The sample of this study consists of firms listed in the Taiwan Stock Exchange from 1996 through 2006. The empirical results in this research are summarized as follows: 1、 The implementation of the Imputation Tax System and a firms' imputation tax credit ratios have a negative impact on the percentage of foreign ownership in listed companies, but the implementation of Alternative Minimum Tax System has a positive impact on that. We conduct further examination and find the increasing effect of the percentage of foreign ownership is more rely on the effect of stock index than that of the implementation of Alternative Minimum Tax System. Further, foreign investors still prefer to invest in listed companies whose effect rates are lower than 10%. 2、With the implementation of Alternative Minimum Tax System, the use of investment tax credit was restricted. The empirical result of this study shows that after the implementation of Alternative Minimum Tax System, the investment tax credit has a negative but not significant impact on the percentage of foreign ownership in listed companies.

本文以除權息前後累積異常報酬率為應變數，探討稅額扣抵比率及股權集中度對除權息前後累積異常報酬率的影響。研究對象為民國88年至96年間分配盈餘的國內上市公司，排除行業性質特殊之金融業，以普通最小平方法從事實證模型分析。主要實證結果彙整如下： 1.稅額扣抵比率與除權息前之累積異常報酬率呈顯著正相關，與除權息後之累積異常報酬率呈負相關，但較不顯著。此表示稅額扣抵比率的租稅因素影響在除權息前較為顯著，但在除權息後現象較不顯著。 2.股權集中度與除權息前後之累積異常報酬率的關係均未達統計上顯著水準。產生此實證結果的可能解釋有二：（1）非稅成本的考量；（2）本文以股權集中度衡量可能並未真正捕捉到個人投資人的所得稅率。 3.低稅額扣抵比率類的除權息前累積異常報酬率，較高稅額扣抵比率（基準）類樣本為低的現象，此與預期相符。但在其他加入類別虛擬變數的迴歸結果，並未發現在不同稅額扣抵比率或股權集中度下，會對除權息前後之累積異常報酬率有不同的影響。 4.公司規模及股價淨值比與除權息前後累積異常報酬率均呈顯著正向關係；股利殖利率與除權息前累積異常報酬率呈顯著正向關係，而與除權息後之累積異常報酬率呈顯著負向關係。電子業別與除權息前之累積異常報酬率呈顯著負向關係，而與除權息後之累積異常報酬率呈顯著正向關係。 在圖表的分析中，可看出高稅額扣抵比率或低股權集中度的樣本，其除權息前後累積異常報酬率波動較小，較不受除權息事件的影響。 / The main purpose of this paper is to examine, before and after the ex-dividend day, the impacts of imputation credits and ownership concentration on cumulative abnormal returns(CARs). In this paper , CARs before and after the ex-dividend day are used as the dependent variable. The data are collected from the domestic listed companies which had allocated the earnings from 1999 to 2006. Because of its special characteristics, the financial industry is excluded from the data. In order to analyze the impacts of imputation credits and ownership concentration on CARs , we used the ordinary least squares. The empirical results in this paper are summarized as follows: 1.The imputation credits have a significant positive impact on CARs before the ex-dividend day, but they don’t have a significant negative impact on CARs after the ex-dividend day. This phenomenon implies that the influence of tax factor before the ex-dividend day is more significant than that after the ex-dividend day. 2.The failure of finding a significant relation between ownership concentration and CARs of before and after the ex-dividend day maybe due to two reasons. Frist, investors may not take tax factor into account when they invest the stock. Second, the proxy variable for ownership concentration of this study may not fully capture the marginal income rate of individuals. 3.CARs before the ex-dividend day in listed company with lower imputation credit are lower than that in listed company with higher imputation credit, the empirical result matchs general intuition. But other regressions with dummy variables regarding the degree of the imputation credit and ownership concentration don’t find significant relation among the imputation credit, ownership concentration and CARs before and after the ex-dividend day. 4.The size of companies and the ratio of market price to their book value have a significant positive impact on CARs before and after the ex-dividend day. Dividend yield has a significant positive impact on CARs before the ex-dividend day, but a negative impact on CARs after the ex-dividend day. A dummy variable standing for electronic industry has a significant negative impact on CARs before the ex-dividend day, but positive impact on CARs after the ex-dividend day. In the analysis of diagrams, we find CARs before and after the ex-dividend day fluctuate less for companies with higher imputed credit or lower ownership concentration.

本論文探討兩稅合一制所增設的兩個機制，即稅額扣抵比率及加徵保留盈餘稅對上市公司股利發放、資本結構以及公司租稅規劃的影響。首先以數學模式推導出兩稅合一制下這兩個機制與股利發放率及負債權益比率之間的關係，再據以建立研究假說，而後進行兩步驟多變量程序之實證測試。研究所獲致的結果包括： 　　一、兩稅合一制實施後，上市公司稅額扣抵比率與總（盈餘）股利發放率呈正相關，且上市公司稅額扣抵比率愈高者，其總（盈餘）股利發放率、現金股利發放率及盈餘配股發放率皆較兩稅合一制實施前高。由於公積配股並不受兩稅合一制實施的影響，故本文也發現兩稅合一制實施前後公積配股率並無顯著差異。整體而言，兩稅合一制實施後，總（盈餘）股利發放率、盈餘配股發放率及公積配股率較實施前減少，而現金股利發放率較實施前增加。進一步的分析顯示現金股利發放率的增加係受到健全股利政策的推行影響，而盈餘配股發放率的減少可能是受到股票股利緩課取消的影響。 　　二、兩稅合一制實施後，符合促進產業升級條例第八條及第九條規定之投資方案，選擇股東投資抵減之公司並無顯著多於選擇五年免稅之公司，可能原因為選擇五年免稅有利於公司現金流量及每股盈餘的金額。此一結果雖與預期方向相反，但也顯示政府原先擔心公司會選擇股東投資抵減而造成鉅額稅收流失的疑慮並未獲得實證支持。但從兩稅合一實施後公司股權結構的變動分析顯示，公司法人持股比率較實施前增加，而僑外投資持股率較實施前減少，支持公司在不同股東身分稅負差距的考量下，會有股權結構移轉之租稅規劃，以降低股東所負擔的稅負。 　　三、兩稅合一制實施後，上市公司稅額扣抵比率愈高者，股東所享扣抵權愈多，則舉債租稅利益愈少，因而總負債權益比率將降低；而上市公司保留盈餘比率愈高者，所課徵的保留盈餘稅愈高，舉債利息的租稅利益反而增加，會造成總負債權益比率增加。本文的實證結果也顯示，兩稅合一制實施後，上市公司稅額扣抵比率愈高者，其總負債權益比率較實施前低；而上市公司保留盈餘比率愈高者，其總負債權益比率較實施前高。 　　綜合本論文實證結果顯示，兩稅合一制實施後，稅額扣抵比率的機制確實其有消除股利所得重複課稅的效益，進而提高公司股利發放的意願，並且有助於公司資本結構的改善。但是，政府對於未分配盈餘加徵 10％營利事業所得稅的規定卻不利於公司資本的累積，反而提高舉債的租稅誘因，也可能抵銷稅額扣抵比率降低舉債的效果，值得政府深入檢討對公司未分配盈餘課稅的不利影響。 / Enacted in 1998, the Integrated Income Tax System has two important features, i.e., the imputation tax credit to shareholders and the 10% surtax levied on undistributed earnings. Using two-step multivariate regression, this study exmines the impacts of these two features on corporations' dividend payout, tax planning, and capital structure. The findings of this study are as follows : 　　1. After implementation of the Integrated Income Tax System, the imputation tax credit ratio is positively related with total dividends payout ratios. Companies with higher imputation tax credit ratios tend to pay out more cash dividends and earnings stock dividends, ceteris paribus. However, there appears no significant relation between the imputation tax credit ratio and capital stock dividends. On average, after implementation of the Integrated Income Tax System, stock dividend payout ratios, including earning stock dividends and capital stock dividends, are decreased, but cash dividend payout ratios are increased. The increase in cash dividend payout may be affected by the balance dividend policy by the SEC, which require corporations to pay out greater proportions in cash dividends. The decrease in earning stock dividends may be due to the cancellation of the deferral of tax on stock dividends. 　　2. After implementation of the Integrated Income Tax System, inconsistent with the expectation, companies still prefer the five-year tax exemption to the investment tax credits. The results suggest that companies' choices are affected more by such factors as corporate cashflows and earnings per shares. However, after implementation of the Integrated Income Tax System, there is a significant change in stockholder structures, with the ratios of corporation stockholders being increased while the ratios of oversea stockholders being decreased. The opportunity of tax arbitrage will have a significant impact on corporations' stockholder structures. 　　3. After implementation of the Integrated Income Tax System, for companies with higher imputation tax credit ratios, their stockholders will have greater tax benefits, and, hence, the tax benefit for companies to use debt financing is decreased. Conversely, companies with higher ratios of retained earnings will bear more tax burdens on the 10% surtax levied on undistributed earnings; therefore, the tax benefit of debt financing is increased. The empirical results support that, ceteris paribus, companies with higher imputation tax credit ratios tend to have lower debt-to-equity ratios, while companies with higher ratios of retained earnings tend to have greater debt-to-equity ratios. 　　In summary, after implementation of the Integrated Income Tax System, the imputation tax credits reduce the double taxation on stockholders' dividend income and, hence, improve corporations' capital structure. However, the 10% surtax on undistributed earnings may result in opposite effect on corporations' capital structure. 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' retained earnings.