This study examines the relationship between internal control system and risk assessment in Board of Internal Revenue in Bauchi State. Data were generated with the aid of necessary information collected from the study through the cross sectional survey through the administered of questionnaire. A total population size of 150 were selected and sample size of 109 was determined using Taro Yamane‘s formula at 0.05 level of significance. Also, 109 copies of questionnaire were distributed to the respondents, while 87 copies were completed and retrieved. The instruments were validated with reliability above 0.8 co-efficient, using Cronbach Alpha Technique. six research questions and six hypotheses were raised which was tested with spearman‘s rank order co-efficient of correlation using SPSS 20 version. From the findings, the concept of internal control system creates positive impact on risk assessment and risk financings. In conclusion, internal control system has a significant impact in risk assessment in the Nigerian public sector. Based on the findings and conclusion, it could be recommended that any internal auditor who cannot demonstrate the appropriate skills and knowledge should not undertake work in the area of risk assessment. Furthermore, internal control system should maintain high level of objectivity and independence in carrying out their core function of evaluating and providing management with assurance on risk assessment.