我國公司邊際稅率模擬研究分析

Abstract

邊際稅率是提供企業者在會計與財務決策之攸關資訊，本研究利用帶趨勢的隨機漫步模式（簡稱隨機模式）與均數迴朔模式（簡稱迴朔模式），考慮營業盈虧後抵之課稅所得，模擬估計邊際稅率。為使模型的理論能有效應用到實務上，本研究以我國上市公司民國八十四年度之模擬估計邊際稅率作探索性研究，提供模擬結果之統計數據及推論。研究結果有四：（1）當公司實際邊際稅率為0%水準時，隨機模式估計的較好;0%至25%水準之間時，迴朔模式估計的較好;而25%水準時隨機與迴朔模式一樣好;（2）當公司實際邊際稅率為0%或25%水準時，法定稅率可以替代估計邊際稅率;0%至25%水準之間時，法定稅率無法替代迴朔模式估計的邊際稅率;（3）無論公司實際邊際稅率為任何水準，有效稅率皆無法替代估計邊際稅率;（4）我國公司平均邊際稅率以當期課稅所得小於零且以往年度有累計虧損的情況最低;當期課稅所得大於或等於零且以往年度無累計虧損的情況為最高，與理論所預期的相符。

Marginal tax rate conveys relevant information for the firms’ financial decision-making. This study aims to estimate marginal tax rates via both random walk with drift model (RWM) and mean reverting model (MRM). Specifically, the settings incorporate taxable incomes with the five-year net operating losses carry-forward. To gain empirical efficiency, I explore the simulated marginal tax rates of 1995 for the listed companies in Taiwan with the test statistics and inferences. The results are four-fold. First, the RWM marginal tax rate (EMTR) estimates are better when the real marginal tax rates (RMTRs) are at the 0% level; the MRM EMTR estimates are better when RMTRs are between 0% and 25% level; both models perform equally well when RMTRs are at the 25%. Second, statutory rates are better substitutes for the EMTRs when RMTRs are at the 0% or 25% level; yet EMTRs by MRM are better substitutes when RMTRs are between 0% and 25% level. Third, the effective tax rates fail to substitute for the EMTRs at any level of RMTRs. Fourth, the study provides evidence consistent with the notion that the corporate marginal tax rate reaches the lowest level at the negative condition of current taxable income with cumulative net operating loss and the highest one at the positive condition with no cumulative net operating loss.