本研究為探討企業異常避稅行為對信用評等之影響，採用 Kim, Mcguire, Savoy and Wilso n (2019) 正常避稅水準之概念，區分出企業異常避稅行為，並分為異常激進與異常保守避稅行為。本研究預期信評機構可能因企業偏離正常避稅水準，進而認為企業未能適當權衡避稅行為產生的租稅利益 、非稅務成本與調整成本，因此判斷債權人承受之違約風險較高 ，而給予較低之評等。本研究以 1993 年至 2016 年之美國上市公司進行實證研究，實證結果支持上述預期，並於敏感性分析中獲得一致性的證據，顯示信評機構非以單一角度檢視企業避稅行為。此外，本研究以橫斷面分析檢視影響異常避稅行為之調節變項，並發現代理風險嚴重與資訊風險較高之企業其異常激進避稅程度與信用評等之負相關將更明顯。

This study explores the impact of corporate abnormal tax avoidance behavior on cr edit ratings. Using the concept of normal tax avoidance level of Kim, Mcguire, Savo y and Wilson (2019) , this study distinguishes abnormal corporate tax avoidance b ehavior and divides it into abnormally aggressive and abnormally conservative ta x avoidance behavior. This study expects that credit rating agencies may believe that the company deviating from the normal level of tax avoidance has failed to properl y weigh the tax benefits, non-tax costs and adjustment costs generated by tax avoi dance; as a result, credit rating agencies judge that the default risk of creditors is hi gher and give a lower rating. This study conducts an empirical study on U.S. listed c ompanies from 1993 to 2016. The empirical results support the above expectations and obtain consistent evidence in the sensitivity analysis, indicating that credit rati ng agencies do not view corporate tax avoidance from a single perspective. In add ition, this study examines the moderating variables that affect abnormal tax avoida nce behavior by cross-sectional analysis, and finds that the negative correlation bet ween abnormal tax avoidance level and credit ratings of companies with severe ag ency risk and higher information risk will be more pronounced.

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