Degefa DuressaKirubel Zeru2026-11-102026-11-102026-05-02https://etd.aau.edu.et/handle/123456789/9462. This study examined the challenges of tax assessment and collection for Category "A" taxpayers in the Arada Sub-City Revenue and Customs Authority Branch Office, Addis Ababa, Ethiopia. The main objective of the study was to identify the major administrative, institutional, legal, and taxpayer-related factors affecting effective tax assessment and revenue collection. The study employed a descriptive research design with a mixed research approach combining quantitative and qualitative methods. Both primary and secondary data sources were used. Primary data were collected through self-administered questionnaires, document analysis, and semi-structured interviews, while secondary data were obtained from books, journals, government reports, and other relevant publications. A stratified random sampling technique was employed to ensure adequate representation of different taxpayer groups. The study population consisted of 3,475 Category "A" taxpayers registered in Arada Sub-City, and a sample of 120 respondents, comprising 100 taxpayers and 20 tax officials, was selected for the study. Reliability and validity of the research instrument were verified using Cronbach's Alpha and KMO and Bartlett's tests, confirming that the questionnaire was appropriate for data collection. The findings revealed that tax assessment and collection are hindered by unclear tax laws and regulations, inadequate administrative capacity, limited technological integration, insufficient taxpayer awareness, weak transparency and accountability, and frequent legislative changes. The study also found that government tax policies and poor communication of policy changes negatively affect tax compliance and revenue collection. The research concludes that improving tax administration requires simplifying tax regulations, strengthening institutional capacity, expanding digital tax systems, enhancing taxpayer education, and improving transparency and accountability. The study contributes to the existing body of knowledge by providing empirical evidence on the challenges facing Category "A" taxpayers in Arada Sub-City and offers practical recommendations for policymakers and tax authorities to improve tax administration and domestic revenue mobilization in Ethiopia.enTax assessmentTax collectionCategory "A" taxpayersTax administrationTax complianceTaxpayer awarenessRevenue collectionArada Sub-CityEthiopiaThesis