This study examined the effect of tax policy reforms on the financial sustainability of Small and Medium Enterprises (SMEs) in Nigeria, focusing on firms listed on the Growth Board of the Nigerian Exchange Group (NGX). The study was motivated by concerns that high tax rates, inefficient tax administration, and limited access to tax incentives continue to constrain SME financial sustainability despite ongoing reforms. The main objective was to assess the effect of tax rate, tax administrative efficiency, and tax incentives on SME financial sustainability, measured by Return on Assets (ROA). A panel research design was employed, relying on primary data collected through structured questionnaires administered to the selected SMEs. Data were analyzed using E-Views software, employing descriptive statistics, correlation analysis, and panel regression techniques, specifically the fixed effects model. The findings revealed that tax rate negatively and significantly affected financial sustainability, while tax administrative efficiency and tax incentives exerted positive and significant effects on ROA. The results indicate that excessive tax burden undermines SME sustainability, whereas efficient tax administration and accessible incentives enhance financial resilience. The study concluded that tax policy reforms significantly shape the financial sustainability of SMEs in Nigeria and recommended rationalization of SME tax rates, improvement of tax administration, strengthening of tax incentives, and consistent policy implementation to support SME growth and long-term sustainability.