T The directorate general of taxes (dgt) has implemented the coretax administration system as part of the digital transformation of taxation in indonesia to establish an efficient, effective, and sustainable tax system and to enhance taxpayer compliance. this final project aims to review and compare the effectiveness of the administration of the deduction, remittance, and reporting of article 23 withholding income tax for the periods of january to december 2024 and january to december 2025. this study employs a descriptive qualitative approach, with data collected through interviews, observations, and tax administration documents. the results indicate that the implementation of the coretax system at pt mni has improved the effectiveness of the administration of article 23 withholding income tax (unified), particularly in terms of process speed, data accuracy, and compliance with remittance schedules. however, this study also identifies several challenges, including limited user understanding and system disruptions that affect the smooth execution of article 23 tax administration processes.