This study analyses fiscal federalism and revenue productivity under India’s Goods and Services Tax (GST) using recent fiscal data and policy developments. Drawing on secondary data from Union Budget documents, GST Council reports, and official government releases, the paper evaluates how GST has reshaped centrestate fiscal relations, revenue sharing, and state fiscal autonomy. Since its introduction in 2017, GST has unified the indirect tax system and expanded the tax base, making it a central pillar of public finance in India. Empirical evidence shows that gross GST collections reached a record ₹22.08 lakh crore in FY 2024–25, registering a 9.4% annual growth, with average monthly collections of about ₹1.84 lakh crore. The registered taxpayer base expanded from about 1.20 crore in 2021 to over 1.45 crore by March 2025, indicating compliance-led revenue growth supported by digitalisation and e-invoicing.The study finds that IGST contributed ₹11.25 lakh crore, or about 51% of total GST revenue, highlighting the growing importance of inter-state trade but also creating settlement dependencies that sometimes led to 4–6 weeks transfer delays and liquidity pressures for states. SGST collections amounted to ₹5.16 lakh crore, strengthening state finances, while the compensation cess balance declined to ₹0.70 lakh crore, signalling transition toward a post-compensation regime. Rising refunds, which crossed ₹2.10 lakh crore (9.5% of gross collections), moderated net revenue gains. Interstate disparities are evident, as high-income states accounted for over 38% of SGST collections. The paper concludes that GST has enhanced revenue buoyancy and cooperative federalism, but sustaining its gains requires timely IGST settlements, efficient refund management, and balanced fiscal equalisation.