財務會計準則規範為因應企業間不同之特性，故允許公司在符合財務會計準則規範下，得選擇最能反映其企業實質之會計原則和方法加以記錄，因而導致不同之會計結果。故本研究旨在探討企業是否確實利用會計方法之可擇性來影響其有效稅率。 本研究係以美國Compustat資料庫中公司自1988年至2003年之財務報表資料，針對會計方法之選擇與其他相關企業特性因素對於有效稅率影響進行實證研究，進而探討美國租稅改革法案TRA 86在實行多年後是否較已達成租稅公平之目標。 經實證結果發現： 一、會計方法與公司有效稅率 採用後進先出法之公司，其公司有效稅率顯著低於採行其他評價方法之公司，而會計估計對於有效稅率之影響，研究中採用提列壞帳之比率及退休金費用兩變數來探討，但皆無法獲得實證證據之支持。 二、公司特性與有效稅率 實證結果發現公司特性之相關變數包括企業規模、投資政策、融資政策等皆與公司有效稅率間呈顯著相關。 三、有效稅率與租稅公平 不同投資政策與融資政策之企業特性在TRA 86後與公司有效稅率間仍存有顯著相關，顯示TRA 86之實施並未確實有效解決企業間差異所造成之問題。 / To account for specific business characteristics, accounting standards allows corporations to choose the most suitable accounting principles and methods to reflect economic substance and then would result in different outcomes. Therefore, the purpose of the study is to assess the extent of the effect of accounting choices on corporate effective tax rates (ETRs). The sample is comprised of American companies in Compustat data bank during the period from 1988 to 2003. The study empirically examines the association of different accounting methods and firm-specific characteristics with effective tax rates. Moreover, the study also examines the tax reform act of 1986 (TRA86) whether it improved the fairness of taxation or not. The empirical results indicate as follows: 1. Corporations adopted Last-in, First-out (LIFO) inventory evaluation method show lower ETRs, suggesting that there is a significantly negative relationship between ETRs and LIFO; conversely, there is no empirical evidence finds that ratio of bad debt and pension expenses are correlated with ETRs. 2. The results show that ETRs are significantly associated with some firm-specific characteristics such as firm size, financing decision, and investing decisions. 3. Because those firm-specific characteristics are still correlated with effective tax rates after TRA 86, the results imply that TRA86 does not fully and effectively resolve the problems of fairness of taxation among corporations.