Bridging the gap: the role of assurance quality in reducing sustainability decoupling

Purpose – This study aims to investigate whether and how assurance quality mitigates sustainability decoupling, understood as the misalignment between corporate environmental, social and governance (ESG) performance and disclosure. Drawing on legitimacy theory, it explores whether high-quality assurance functions as a substantive mechanism that enhances transparency and credibility in sustainability reporting or a symbolic tool aimed at managing stakeholders’ perceptions. Design/methodology/approach – The analysis relies on a panel of 717 European companies (6,925 firm-year observations) from 2014 to 2023. A panel Tobit model with random effects was estimated, complemented by robustness checks using linear regression with fixed-effects, random-effects and generalized method of moment estimators. Findings – The results reveal that higher assurance quality – characterized by broader scope, comprehensive content, higher assurance level, multi-method approach and use of recognized standards – significantly reduces ESG decoupling, supporting the substantive legitimacy perspective. Originality/value – This study enriches the literature on sustainability decoupling by examining assurance quality as an external accountability mechanism and extends the application of legitimacy theory tosustainability assurance practices.