Heterogeneous Maturity Patterns in India's BRSR Disclosure: Three-Year Longitudinal Assessment with ICAI-CRISIL Validation

This study examines the evolution of sustainability reporting among Indian corporations following the Securities and Exchange Board of India's (SEBI) mandatory Business Responsibility and Sustainability Reporting (BRSR) implementation. Guided by three testable hypotheses, we investigate how the regulatory transition from voluntary Business Responsibility Reports (BRR) to mandatory BRSR has influenced disclosure quality, sectoral performance patterns, and the validity of assessment frameworks. Using the Institute of Chartered Accountants of India (ICAI) Sustainability Reporting Maturity Model (SRMM) Version 2.0, we conduct a comprehensive longitudinal assessment of 28 NSE-listed companies across eight sectors over three consecutive financial years (FY 2021-22, FY 2022-23, and FY 2023-24), comprising 84 company-year observations. Our research tests three hypotheses: H1 (disclosure quality increases over time), H2 (sectoral performance heterogeneity), and H3 (strong convergent validity with external ESG ratings). Our findings provide strong empirical support for all three hypotheses. For H1, maturity analysis reveals progressive quality enhancement: Level 1 (Formative) maturity declined from 10.7% to 3.6%, while Level 4 (Leading) maturity increased from 14.3% to 25.0%, with 67% of companies advancing to higher maturity levels. Mean BRSR scores improved significantly from 52.3% to 64.8% (+12.5 percentage points, +23.9% relative improvement, p < 0.001). For H2, sectoral analysis confirms statistically significant differences (F(7,20) = 8.45, p < 0.001, η² = 0.75). Information Technology (74.5%) and Banking & Financial Services (71.9%) demonstrated consistent leadership throughout the study period, while resource-intensive sectors (Oil & Gas: 52.0%, Metals & Mining: 55.6%) showed persistent disclosure challenges. The 22.5 percentage point gap between highest and lowest performers (IT: 74.5% vs. Oil & Gas: 52.0%) confirms substantial sectoral heterogeneity. For H3, we find exceptionally strong correlation between ICAI SRMM 2.0 maturity scores and independent CRISIL ESG ratings that strengthened progressively over three years (FY 2021-22: r = 0.901; FY 2022-23: r = 0.928; FY 2023-24: r = 0.944, R² = 0.891, all p < 0.001). This validates that BRSR framework implementation enhances disclosure quality and reflects substantive ESG performance improvements. The R² improvement from 0.812 to 0.891 (+7.9 percentage points) demonstrates framework maturation and organizational learning effects. Dimensional analysis reveals heterogeneous improvement patterns: Social dimension showed strongest gains (+13.7% absolute, +25.3% relative), followed by Governance (+13.5% absolute, +23.8% relative), and Environmental (+8.1% absolute, +16.8% relative). Despite overall improvements, critical disclosure gaps persist: Climate Transition Planning (80% inadequate), Scope 3 Emissions (70% inadequate), and Third-Party Assurance (75% lacking). This research provides the first empirical validation of ICAI SRMM 2.0 through longitudinal application and external rating correlation, offering evidence-based insights for regulators seeking to enhance mandatory disclosure effectiveness, corporations pursuing disclosure excellence, and investors evaluating ESG performance in India's evolving sustainability reporting landscape. JEL Classification: M14 (Corporate Culture; Social Responsibility), G34 (Corporate Governance), Q56 (Sustainability)