This study aims to evaluate the internal control system which is guided by government regulation number 60 of 2008 concerning the government's internal control system and are to investigate the factors which influence the realization of revenue on the land and building taxes in district kolaka. This research was conducted at the Tax Management Agency and Regional Retribution of the district kolaka. The data analysis method used in this research is descriptive analysis method. The type of data used in this study is qualitative, qualitative data in the form of questionnaires. The method of data collection uses questionnaire and interview methods. The results of this study indicate that the percentage of the internal control system is categorized as adequate with a value of 80.19%. The percentage obtained by each indicator, namely for the Control Indicator Environment is categorized as adequate with a value of 64,24%. The Risk Assessment Indicator is categorized as adequate with a value of 66,56%. The Indicator of Control Activities is categorized as very adequate with a value of 97,65%. Information and Communication indicators are categorized as very adequate with a value of 81,24%. Monitoring indicators are categorized as adequate with a value of 73,12%. Overall, the five indicators show a adequate category, which is 80,19%. The percentage of the local tax admissions system is categorized very according to the value of 100,00%. The percentage obtained by each indicator, namely for the Registration & Data Indicator is categorized as very suitable with a value of 100,00%. Determination indicators & objections are categorized as very suitable with a value of 100.00%. Billing Indicators are categorized as very suitable with a value of 100.00%. Overall, the three indicators show very suitable categories, namely 100,00%. The lack of realization of land and building taxes in district kolaka is caused by several external factors, namely: (1) Lack of public awareness. (2) Taxpayers do not reside in the tax object. (3) Taxpayers ' home tenants or only while occupying tax objects. (4) Taxpayers are not recognised. (5) The Taxpayer name error in Notification of Tax Due (L&B Tax). (6) The Tax object address does not match the actual condition.