This study examines the year-on-year percentage change in Goods and Services Tax (GST) collections across five South Indian states—Karnataka, Kerala, Tamil Nadu, Telangana, and Andhra Pradesh—from 2017–2018 to 2023–2024. Employing a comparative and trend analysis framework, the research traces the initial post-implementation surge, the pandemic-induced contraction, and the subsequent recovery and deceleration phases. While all states experienced robust growth immediately after the introduction of GST, the subsequent trends reveal significant divergence. Karnataka consistently outperformed its peers, benefiting from digital readiness and administrative efficiency, whereas Andhra Pradesh, despite an early lead, now lags. The findings highlight the influence of state-specific economic structures, governance models, and digital infrastructure on tax performance.