稅務訴訟未納入專業審理機制，本研究藉由司法院以經驗為基礎的專業久任規定，探討法官專業化對稅務訴訟的影響。透過門檻指標內生轉換模型的結果顯示，一般法官審理所得稅與營業稅訴訟時，會計師訴訟績效及效率皆優於律師；未發現律師與會計師在專業法官審理能明顯影響訴訟績效。本研究進一步考量會計事項樣本發現，一般法官審理會計事項二稅案件，會計師績效表現反而不佳。一般法官缺乏審理系列案件經驗，代理人取得勝訴機率皆未超過5%；專業法官審理時，會計師訴訟績效佳，且訴訟效率與效果皆優於律師。本文實證結果呈現，法官藉由審理經驗專業化養成，可強化二稅案件審理的決策行為，而會計師在會計事項案件，則顯露出專業的訴訟代理角色。

This paper examines the experience effect of judges professionalization on agent's tax litigation performance. We employ the endogenous switching regression model with unknown sample separation to classify experienced judges on income- and business-tax litigation into the professional judges regime. The empirical result shows that Certified Public Accountants (CPAs) perform better than attorneys when the judges lack related tax litigation experiences. On the other hand, we do not find significant performance differences between CPAs and attorneys in the regime of professional judges. The accounting issue subsample test of tax litigation, the professional judges regime sample indicates that CPAs have better litigation performance than attorneys, and also perform advantage in litigation effect and efficiency. In contrast, CPAs perform worst in litigation performance, and both CPAs and attorneys have trail-win rates extremely under the 5% by the judges who lack of experiences. In sum, judges' experience is important for the legal system, and CPAs play a role of professional agent in the tax litigation.