Professional Assessment of Corporate Sustainability Reporting Quality in Nigerian Quoted Companies

Corporate sustainability reporting is increasingly demanded by investors and regulators in Nigeria, and professional assessment of its quality among quoted companies provides evidence for reporting standard improvement. This study assessed the quality of sustainability reports published by 30 companies listed on the Nigerian Exchange Group between 2021 and 2023, covering banking, oil and gas, consumer goods, and telecommunications sectors. Report quality was assessed using a modified GRI Standards Index covering environmental disclosures, social performance reporting, governance transparency, economic impact communication, and third-party assurance quality. Content analysis and report scoring by trained assessors were employed, and quality scores were correlated with company size, sector, and profitability. Results showed that oil and gas companies had the highest sustainability reporting quality scores (mean: 68.4 out of 100), attributed to regulatory reporting requirements under the Petroleum Industry Act. Banking sector scores were moderate (mean: 58.7), while consumer goods companies were weakest (mean: 44.2). Third-party assurance was obtained by only 37% of reporting companies. Environmental disclosure was the weakest reporting dimension across all sectors (mean: 41.3). Company size was significantly positively correlated with reporting quality (r = 0.61, p < 0.001), with large companies outperforming SMEs. The study concludes that sustainability reporting quality in Nigerian quoted companies is improving but remains below global standards, and recommends mandatory GRI-aligned sustainability reporting for all NGX Premium Board companies with Securities and Exchange Commission enforcement oversight. Keywords: sustainability reporting, corporate disclosure, Nigerian Exchange Group, GRI standards, ESG