Tax is considered as the largest contribution of income for the state which is used for the needs of the state for the welfare and prosperity of the citizens. However, a lot of taxpayers still are not obedient in fulfilling their tax obligations. This happens because they adopt a belief of paying tax can reduce their income without thinking of the importance of tax to the state. This research aims to study the effect of tax sanction, taxpayer awareness, and tax assessment system on individual taxpayer’s compliance at KPP Pratama Medan Belawan. This research is a quantitative descriptive approach using primary data in the form of a questionnaire. The sampling method used is the accidental sampling method with 100 samples out of a total population of 90.379 registered individual taxpayers. The analysis model used in this study is a multiple linear analysis model and processing data in this study is using the SPSS version 25 program. The results of this study indicate that partially, tax sanctions has a positive and significant effect on individual taxpayer’s compliance, taxpayer awareness has a positive and significant effect on individual taxpayer’s compliance, and tax assessment system has a positive and significant effect on individual taxpayer’s compliance. Simultaneously, tax sanction, taxpayer awareness, and tax assessment system have a positive and significant effect on individual taxpayer’s compliance.