T This study analyses tax compliance during the implementation of indonesia\\\'s core tax administration system (coretax) through the slippery slope framework. it examines how the power of the tax authority, taxpayers\\\' trust in government, perceived fairness of the tax system, and tax education shape compliance duringthe transition to an integrated digital tax administration. the research applies a qualitative exploratory case-study design. data were collected through semistructured interviews with six informants comprising tax practitioners or consultants, company executives and staff, a micro, small and medium enterprise actor, and private-sector employees who had experience with or exposure to coretax. the data were analysed using thematic analysis supported by nvivo. the findings indicate that coretax can improve data integration, administrative documentation, transparency, and the supervisory capacity of the directorate general of taxes. nevertheless, during the transition period, compliance is still perceived predominantly as enforced rather than voluntary. third-party data integration and automated administration strengthen the power of authority, butthey also create concerns regarding inaccurate data, misclassification of transactions, automatic sanctions, and an imbalance in the taxpayer-authority relationship. trust in authority is conditional upon system stability, data accuracy, understandable information, responsive assistance, and the government\\\'s ability to protect taxpayers when problems originate from the system. perceived fairness is mainly influenced by the availability of correction rights, clarification channels, balanced evidentiary burdens, proportional sanctions, and effective disputeresolution mechanisms. tax education plays a bridging role by helping taxpayers understand digital supervision, exercise procedural rights, and adapt to new processes. the study concludes that sustainable tax compliance under coretax requires a balance between effective authority, institutional trust, procedural fairness, user-oriented digital services, data protection, and continuous tax education.