The reliance of the government budget on oil revenues represents a structural challenge in Iran's economy, significantly impacting economic stability and public welfare. Consequently, reforming the tax system, particularly the tax bases, as the most sustainable source of government revenue, is of undeniable necessity. This study aims to identify and prioritize the issues and solutions for reforming tax bases in Iran. To achieve this objective, a qualitative approach based on content analysis of documents and library studies was employed, followed by semi-structured interviews with tax experts to compile a set of issues, challenges, and solutions for reforming tax bases. Subsequently, the Analytical Hierarchy Process (AHP) technique was used to prioritize these issues and solutions. The research findings show that 1) inefficiency of tax exemptions and incentives, 2) weakness and inefficiency of tax laws and regulations, 3) inappropriate structure of tax rates, 4) lack of attention to expanding new tax bases, and 5) weakness and inefficiency in implementing tax laws and regulations are the most important issues and problems of tax bases. Also, prioritizing solutions for reforming tax bases includes: 1) organizing and reforming tax exemptions, 2) reforming existing tax bases, 3) expanding new tax bases, 4) reforming tax laws and regulations, 5) reforming the structure of tax rates, and 6) improving the implementation of tax laws and regulations. Accordingly, it is recommended that policymakers take practical steps toward achieving tax justice and increasing sustainable government revenues by targeting tax exemptions, updating and expanding tax bases, and simplifying tax laws.