This research was being conduct at CV. Cahaya Maju Bersama. This is a trading and distributor company in Tanjung Morawa, North Sumatera that engaged in the distribution of tires products such as inner tubes and outer tires of motorcycle. The objective of this research is to acknowledge the integrity and accuracy of the company’s tax systems and process whether the calculation of corporate income tax has been suitable with the tax regulations specifically with the provision of Law no. 36 of 2008 on Income Tax. The research was conduct through a case study at CV. Cahaya Maju Bersama using the data of fiscal financial statement, payment and report date of income tax article 25 in 2017 and all information that can be use to support the study. Conclusion of this research is that the company has done some errors in fiscal reconciliation in terms of the classification of deductible expenses and non-deductible expenses. This affects to the positive correction for telephone expense of Rp 892,981.00, tax penalty of Rp 114,817.00, as well as other expenses amounting to Rp 15,153,721 should be excluded from the total amount of expenses since it was expense that has no direct relationship with the business activities. And it is by then affecting the amount of income tax payable after tax review will result higher than before tax review such as different from Rp 68,633,592.00 to Rp 71,331,532.00. And it will lead to underpayment of tax amounting to Rp 2,697,940.00.