This study aims to investigate the influence of awareness, knowledge and understanding, quality of service on the willingness to pay tax. The independent variable of this study are the awareness, knowledge and understanding, and service quality, while the dependent variable is the willingness to pay tax. The populations of the study were 29.368 registered taxpayers in KPP Pratama Medan Barat. The research samples were drawn using sampling techniques and it was obtained that there were 100 convenience Taxpayers sampled. This study used Quantitative Research, the nature was quantitative with analytical research, using primary and secondary data sources. Data were collected by means of direct observation using multiple linear analysis using of F test and T- test at significance level of 5% and Adjusted R square was 21.5% change in the willingness to pay taxes variable (Y) is explained by changes in awareness (X1), knowledge and understanding (X2), service quality (X3). The results of this study showed that simultaneously awareness, knowledge and understanding, service quality have a significant effect on the willingness to pay taxes. And partially, they have a significant effect on the willingness to pay taxes on KPP Pratama Medan Barat.