This study aims to investigate the contingent effect of domain knowledge in two different client financial reporting strategy toward tax consultants decision making. The study differentiates the consultants' decision into tax recommendation and willingness to sign clients" tax return. To accomplish this purpose, study participants were given the role of asa tax consultant in a tax compliance task setting. The Experiment was conducted toward experienced students. The results show that tax consultants who posses higher domain knowledge suggest more conservative recommendation when their client adopt aggressive reporting strategy.Furthermore, there is no significant difference in tax recommendation between tax consultant who posses higher and lowers domain knowledge if their client adopts a neutral reporting strategy. Then, the study results show that tax consultants who posses higher domain knowledge have a lower willingness to sign clients tax return when their client adopt aggressive reporting strategy. Lastly, itfound a similar condition has occurred in the neutral reporting strategy condition. These findings suggest that domain knowledge is crucial to solving a variety of client condition. These findings imply the importance of domain knowledge in tax professional work environment. Thus, tax professionals need to be more concern about their domain knowledge when providing tax services.