ABSTRACT:- This study examines the moderating role of audit firm size in the relationship between firm leverage, capital intensity, and sustainability reporting among listed consumer and industrial goods firms in Nigeria. Firm leverage is proxied by the debt-to-equity ratio, capital intensity by the ratio of total assets to total sales, and sustainability reporting by an aggregate ESG disclosure score. Using an ex-post facto, longitudinal panel design, the study draws on a purposively selected sample of twenty-five of thirty-three listed consumer and industrial goods firms with consistent audited annual reports from 2013 to 2025. Panel multiple regression, estimated with E-Views 13, was used to test the hypothesised relationships. The results show that both the debt-to-equity ratio and the capital intensity ratio have a significant effect on ESG disclosure, and that audit firm size significantly moderates these relationships. The findings suggest that capital structure and asset-intensity decisions are important drivers of sustainability disclosure quality, and that the assurance credibility of high-tier (Big 4) audit firms strengthens this effect. The study contributes to the limited empirical evidence on the leverage-capital intensity-ESG nexus in an emerging-market context and extends legitimacy and signalling theory by identifying external assurance quality as a boundary condition. The findings carry implications for market regulators, audit oversight bodies, and corporate boards seeking to strengthen sustainability disclosure practices in Nigeria and comparable emerging economies.

Keywords: Firm Leverage, Capital intensity, Debt ratio, Capital intensity ratio, Sustainability reporting, ESG, Audit firm size, Firm Age.