Intellectual Capital Structure and Sustainability Accounting Disclosure: A Study of Nigerian Listed Non-Financial Firms

Sustainability accounting disclosure by Nigerian listed non-financial firms remains selective, and little is known about which internal resources drive it. This study examined the effect of intellectual capital, measured through human capital efficiency, structural capital efficiency and relational capital efficiency under a modified Value-Added Intellectual Coefficient (VAIC) framework, on sustainability accounting disclosure. Secondary panel data were taken from the annual reports of 74 listed non-financial firms across ten Nigerian Exchange Group subsectors from 2015 to 2024, yielding 696 firm-year observations from an unbalanced panel. Disclosure was scored with a content-analysis index based on the Global Reporting Initiative Standards. The Feasible Generalised Least Squares (FGLS) estimator was used to account for panel heteroskedasticity. Human capital efficiency had a significant negative effect on disclosure, structural capital efficiency had no significant effect, and relational capital efficiency had a significant positive effect. Firm size and firm age were positively related to disclosure, while leverage was not significant. The relationship between intellectual capital and sustainability disclosure therefore differs by component, and relational capital is the only component associated with higher disclosure. The explanations offered for the negative and insignificant results are interpretations that need further testing with direct measures of managerial orientation and sustainability governance. The findings are relevant to regulators and firms preparing for mandatory IFRS S1 and S2 adoption in 2028.