As the financial conditions from all over the world sharply worsened due to the increase in demand about the welfare and international depression, it became important to ensure that public finances corresponding to this. The interest about the plan that can improve the tax compliance of the taxpayer such as legalizing the underground economy with the solution about this matter is rising. The various uncertainties can exist due to the ambiguity of the Tax law and complexity in order to fulfill the liability to pay taxes. This uncertainty can have an effect on the good-faith filing of the taxpayer. This study has estimated the effect of the withholding tax adjustment on the taxpayers’ tax compliance. The tax professionals were selected for test subjects, for most of tax determinations for individual businesses are made by them. And since the tax audit probability by taxation authorities affects the decision-making for taxation, the tax audit probability has been added as a treatment variable. The purpose of this research is to figure out what effect the interim prepayment by taxpayers and the tax audit probability by taxation authorities have on tax professionals’ decision-making. The reviews of Prospect Theory and Regulation Theory enable the anticipation of what effect the amount of interim prepaid tax amount has on the final tax determination. The former argues that individuals act based on the situation-dependent value function measured as gain or loss from the reference point. Concretely speaking, in an uncertain situation, they show aggressiveness in a loss-situation and conservativeness in a gain-situation based on each reference point. Most of studies employing Prospect Theory applied taxpayers’ prepayment position for analyses with the subjects of taxpayers or students. That is, as seen at the anticipation by Prospect Theory, there exists the possibility for the interim prepayment position to have some effects on the final tax decision-making. However, since it is not clear if the situation of taxpayers’ interim prepayment may be the reference point for decision-making, the anticipation of Prospect Theory may not hold any validity. On the other hand, according to Regulation Theory, regulations bring regulated parties some benefit and since the tax professionals, who are regulated groups, have the capability to interpret tax law as the benefit to taxpayers and offer services with diverse scopes as well as negotiate with taxation authorities, they show an aggressive tendency in an ambiguous situation. Due to these traits of tax professionals, there is the possibility that the decision-making by tax professionals may not be affected by whether taxpayers are in an situation where they have to make additional payment or they are supposed to be refunded based on the amount of interim prepayment. Like this, there co-exist two possibilities that the interim prepayment position may have some effect on the final tax determination based on Prospect Theory or not on the ground of Regulation Theory. With experimental method, tax professionals working at accounting firms, tax corporations and private accounting offices were asked to make decisions in virtual taxation situations related to the appropriation of the necessary expenses for damages. For hypothesis testing, the interim prepayment position(balance-due position vs. refund position) and the tax audit probability (low vs. high) have been divided into two levels to be designed as the total of 4 groups. This study has found out that while at the decision-making for appropriating necessary expenses for damages both the customers’ prepayment position and the tax audit probability were influenced as anticipated, only the tax audit probability was statistically significant. The study subjects were selected “private business income earners” whose interim prepayment amount can be adjusted and due to the high dependence on tax professionals. The difference of test subjects may result in the conclusions different from those of preceding researches with taxpayers as the subjects. Moreover, the conclusion is likely to be drawn that since from the taxpayers’ position it may be unclear if the reference point at Prospect Theory is any prepayment position and again because from the tax professionals’ total tax payment can be considered to be more important than the interim prepayment amount, the interim prepaid tax amount has no effect on the decision-making by tax professionals. However, since the conclusion has been drawn that unlike in taxpayers’ prepayment position the tax professionals consider any tax audit probability when they make any decision, it can be utilized as an effective measure controlling tax professionals. These study results indicate there may exist the possibility that when taxpayers’ prepayment position is turned to the refund position, the anticipation for tax compliance to be improved may be wrong even if the difference among test subjects and reference points is to be taken into consideration. Since this study with the application of the existing Prospect Theory suggest the results different from those of most other researches, it is necessary to be complemented through additional researches with various test subjects and reference points considered for its generalization. In addition, since this research has been carried out with experimental methods, it can’t help having the limitations. Even though the tax professionals should have been tested in the controlled environments of certain time and space for higher internal validity, the realistic restraints made it inevitable to carry out the tests with questionnaires. Consequently, the perfect control of environments was not possible. Furthermore, besides the control variables employed at this study, those factors which may affect on the judgment and decision-making of tax professionals might have been omitted. Therefore, there will take care to generalize the results of this study.