Corporate Tax Aggressiveness and Shareholder Value of Listed Nigerian Firms

Corporate tax aggressiveness remains one of the most contested corporate finance phenomena in emerging markets, where institutional voids, regulatory inconsistencies, and weak enforcement create fertile conditions for aggressive tax planning. This study examines the effect of corporate tax aggressiveness on the shareholder value of listed Nigerian firms, using a comprehensive panel dataset of 151 firms listed on the Nigerian Exchange Group (NGX) over the period 2011 to 2025, yielding 2,271 firm-year observations. Tax aggressiveness is operationalised using the effective tax rate (ETR) and book-tax difference (BTD), while shareholder value is measured through Tobin's Q, return on equity (ROE), and earnings per share (EPS). The study controls for firm size, firm age, board size, board independence, industry type, CEO tenure, financial leverage, and ownership structure. Grounded in agency theory, stakeholder theory, and the political cost hypothesis, the study employs pooled ordinary least squares, fixed effects, and random effects panel regression models, with the Hausman test confirming the superiority of the fixed effects estimator. Findings reveal that corporate tax aggressiveness exerts a significant negative effect on shareholder value, suggesting that, in the Nigerian context, the reputational, regulatory, and agency costs associated with aggressive tax behaviour outweigh the anticipated cash flow benefits. Board independence and institutional ownership positively moderate firm value, while financial leverage exerts a significant negative effect. The results are robust to alternative specifications, post-estimation tests, and heteroscedasticity-consistent standard errors. This study contributes to the sparse empirical literature on tax aggressiveness in sub-Saharan Africa and provides actionable implications for policymakers, investors, and corporate governance practitioners.