India’s mandatory corporate social responsibility (CSR) regime under the Companies Act 2013 represents a distinctive legislative model that converts qualifying corporate social expenditure into a statutory obligation. This article examines the impact-assessment framework governing that regime and its evolution through the 2021, 2025 and 2026 regulatory developments, asking whether the legal architecture advances substantive accountability or primarily secures procedural compliance. The research problem concerns the gap between mandatory expenditure and demonstrable social outcomes, particularly in light of fragmented methodologies, uneven evaluator capacity, limited standardisation, and weak mechanisms for measuring long-term change. Employing a doctrinal-cum-analytical and socio-legal approach, the article analyses the Companies Act, delegated legislation, Ministry of Corporate Affairs guidance, comparative sustainability frameworks, and implementation literature. It finds that the post-2021 regime cannot accurately be characterised as a mere “comply or explain” model: where prescribed CSR expenditure remains unspent, the company must disclose reasons and comply with statutory transfer requirements, while defaults in such transfers attract monetary penalties under section 135(7). However, the law does not impose comparable consequences merely because a completed project produces weak or ineffective social outcomes. The study further identifies methodological discretion, assessment-cost constraints, the requirement that qualifying projects be completed at least one year before assessment, and the absence of uniform evaluator-accreditation standards as continuing barriers to reliable and comparable impact measurement. Rule 4A, introduced in 2026, permits limited CSR expenditure through zero coupon zero principal instruments on the Social Stock Exchange and exempts the subscribing company from Rule 8(3) impact assessment for projects funded through that route, while the SEBI Social Stock Exchange framework separately subjects listed projects to impact and utilisation disclosures. Comparing India’s expenditure-centred model with disclosure-oriented sustainability regimes, the article recommends standardised sectoral methodologies, assessor accreditation, stronger board-level responsibility, longitudinal evaluation, and closer integration with sustainable-development indicators.