以融资融券交易为对象，本文分析了卖空威胁对公司避税行为的影响在探讨因果关系可识别性的基础上，通过控制自选择偏误，本文采用双重差分模型检验发现：开通融券交易带来的卖空威胁能够抑制管理者避税行为，这一抑制效果对管理者持股的公司更显著进一步研究发现卖空威胁对避税行为的抑制受公司外部环境影响具体而言，当公司所处省份税收征管强度较低时，抑制作用更显著后续证据显示，激进的避税行为确实能够吸引融券交易者的卖空兴趣，但并未作为融资交易者的决策依据，因而开通融资融券对管理者避税行为的抑制主要来自卖空威胁.最后，作为避税活动减少的后果，本文发现标的公司的信息不透明程度显著降低.

Taking the staggered introduction of margin purchasing and short selling pilot program in China as a natural experiment, this study tests its influence on managerial tax avoiding activities. We establish our tests on detailed discussions about the self-selection problems in our setting and use a difference-in-difference method to identify the casual link. The results revel that the introduction of margin trading and short selling pilot program has significant monitoring effects on corporate tax avoidance. Tax avoiding activates experience a significant reduction after firms are selected into the pilot program. In addition, the phenomenon is more pronounced for firms whose managers hold shares and thus face direct wealth loss resulting from short selling. Also, we find that the phenomenon is more pronounced when firms are operated in looser tax enforcement areas. Further evidence shows that short sellers do target firms with aggressive tax avoiding activities while margin purchasers exhibit no trading interests, and thus the effect of the pilot program on tax avoidance can be safely attributed to the short selling threats. Finally, as the natural consequence of the reduction of complicated tax avoiding activities, we find pilot firms enjoy a more transparent information environment.