本文以實證研究方式，比較兩稅合一前後各三年上市與上櫃公司之有效稅率，探討影響我國公司有效稅率之因素，並檢視有效稅率之影響因素是否隨兩稅合一的實施而有顯著的改變。有關實證模式之建立，除了參考國外相關文獻，如企業規模、投資及理財政策、獲利能力及產業別等決定因素外，並考量我國特殊之稅法規定(證券與土地交易所得免稅)與集團企業經營之特色。
實證結果如下:1. 有效稅率與企業規模、舉債融資、研發支出、長期股權投資呈顯著負相關；與獲利能力、保留盈餘比例呈顯著正相關。兩稅合一實施前後，這些解釋變數與有效稅率關係並無改變。2. 證券、土地交易所得較高公司，有效稅率較低，顯示公司會透過證券、土地交易安排規避稅負；而集團企業有效稅率相對較低，顯示集團企業確實有租稅之優勢。3. 兩稅合一實施對於我國上市上櫃公司有效稅率有顯著影響。公司平均有效稅率在稅制改變後明顯增加，顯示政府在公司階段之稅收增加；但各產業租稅負擔不一致的情況並無改善，也顯示各產業租稅負擔仍存有不公平現象。4. 兩稅合一實施後，企業負債融資比率沒有顯著降低，且與有效稅率仍呈顯著負相關，顯示兩稅合一未達成消除企業籌措財源偏好舉債目的。5. 企業規模與長期股權投資在稅制改變後顯著增加，顯示兩稅合一實施後企業有較高投資意願，且資本市場規模也擴大。6. 電子業在兩稅合一後有效稅率仍然低於其他產業，顯示稅制改變並未影響電子業在租稅上優勢地位。

This thesis empirically examines the effective tax rates (ETRs) of listed and over-the-counter companies for the three years before and after implementation of the integrated income tax system. This thesis investigates the determinants of corporate ETRs in Taiwan and examines whether these determinants have significantly changed with the implementation of the new tax system. The empirical model of this study not only refers to determinants in prior literature such as firm size, investment and finance policies, profitability, and industry, but also considers Taiwan’s unique income tax sys-tem (e.g., tax-exempt income on stock and land capital gains) and business environment (e.g., group companies).
The results of this study are as follows: There is a negative relationship between ETRs and firm size, leverage, R&D, and long-term investment. Conversely, there is a positive relationship between ETRs and profitability and undistributed earnings. These relationships remain unchanged after implementation of the new income tax system. Companies with greater stock and land capital gains tend to have lower ETRs, suggest-ing that the tax exemption on the two capital gains has a significant impact on corpora-tions’ tax burdens. Moreover, group companies tend to have lower ETRs, indicating that corporate affiliations have important tax advantages. The implementation of the Inte-grated Income Tax System has a significant effect on corporate tax burdens. There is a significant increase on the average ETR after the tax reform. However, the inequitable tax distribution across industries has not yet eliminated with the implementation of the new tax system. After implementation of the new tax system, the results show that cor-porate leverage is not decreased and still has a significant impact on lowering ETRs, indicating that companies still favor debt financing. Corporate total assets and long-term investments have significantly increased after implementation of the Integrated Income Tax System, suggesting that the tax reform has stimulated corporate investments and expanded the capital market. Nevertheless, under the new tax system, electronic indus-try still has a significant lower ETR than other industries. Therefore, the tax reform has not fully achieved the goal of leveling the playing field for enterprises.

中文摘要　．．．．．．．．．．．．．．．．．．．．． iii
英文摘要　．．．．．．．．．．．．．．．．．．．．． iv
誌謝辭　　．．．．．．．．．．．．．．．．．．．．． vi
內容目錄　．．．．．．．．．．．．．．．．．．．．． vii
表目錄　　．．．．．．．．．．．．．．．．．．．．． viii
圖目錄　　．．．．．．．．．．．．．．．．．．．．． ix
公式目錄　．．．．．．．．．．．．．．．．．．．．． x
第一章　　緒論．．．．．．．．．．．．．．．．．．． 1
　　第一節　　研究動機與目的．．．．．．．．．．．． 1
　　第二節　　研究架構．．．．．．．．．．．．．．． 2
第二章　　文獻探討．．．．．．．．．．．．．．．．． 5
　　第一節　　我國兩稅合一制度簡介．．．．．．．．． 5
　　第二節　　國外文獻．．．．．．．．．．．．．．． 6
　　第三節　　國內文獻．．．．．．．．．．．．．．． 13
第三章　　研究方法．．．．．．．．．．．．．．．．． 19
　　第一節　　假說之推論．．．．．．．．．．．．．． 19
　　第二節　　實證模型與變數之定義．．．．．．．．． 27
　　第三節　　資料來源與樣本選取．．．．．．．．．． 32
第四章　　實證結果與分析．．．．．．．．．．．．．． 37
　　第一節　　樣本一般敘述性統計量．．．．．．．．． 37
　　第二節　　統計迴歸結果與分析．．．．．．．．．． 45
第五章　　結論與限制．．．．．．．．．．．．．．．． 57
　　第一節　　結論．．．．．．．．．．．．．．．．． 57
　　第二節　　研究限制．．．．．．．．．．．．．．． 59
參考文獻　．．．．．．．．．．．．．．．．．．．．． 60

一、中文部分
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李新仁，周添城，徐偉初(1989)，不同企業規模、組織之稅賦分配研究，財政部賦稅改革委員會專題報告，(6)。
林世銘，張天勳，陳明進(2001)，證券及土地交易所得免稅對我國公司有效稅率之影響，中華會計學刊，2(4)，33-56。
林世銘，黃德芬，劉啟群(2001)，台灣上市公司有效稅率決定因素之研究，中華會計學刊，2(4)，57-84。
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