This study is about the recent Excise Tax Reform. Knowing which components of the new law contribute to its complexity, enforceability, and tax revenue is critical for tax offices to be effective in implementation. The studyâ€™s general objective is to assess the challenges and opportunities of new excise tax law implementation at federal large taxpayersâ€™ branch office. To achieve this objective the research used a survey questionnaire and semi-structured interviews to gather primary data. Part of the results from the primary data was verified and confirmed using secondary data concerning excise tax following the reform. A stratified random sampling technique was also used. The challenges and opportunities of the new excise tax law implementation were identified utilizing a concurrent triangulation strategy of the mixed research approach, which included responses from 109 LTO tax office personnel and purposively selected interviewees. To analyze the data, the researcher used SPSS software (version 20) and descriptive statistics like percentages and tables. The findings of this study indicate that following the reform, in 2019/2020 the excise tax contribution to the branchâ€™s overall revenue increases to 10.02 percent from 7.56 in 2018/2019. However one of the peculiar challenges of the excise tax reform is that the infrastructure required ensuring effective taxation of excises and that Ethiopia now lacks the essential infrastructure to fully implement the law. As a result, the study recommended the Ministry of Revenue to establish an excise tax department that would be fully responsible for the law's effective implementation.