This study examines the effect of financial characteristics namely inventory intensity, sales growth, and leverage on tax avoidance, while assessing the role of firm age as a mediating variable. Motivated by inconsistent prior findings and limited attention to firm age as an intervening mechanism, the study uses panel data from 44 consumer non-cyclicals firms listed on the Indonesia Stock Exchange over 2020–2024 (220 firm-year observations). The analysis employs Partial Least Squares Structural Equation Modeling (PLS-SEM) using SmartPLS, complemented by covariance-based Structural Equation Modeling (CB-SEM) in Stata for robustness. The results show that leverage and inventory intensity have a positive and significant effect on the Effective Tax Rate (ETR), indicating lower levels of tax avoidance, while sales growth has no significant effect. Firm age is not found to significantly influence tax avoidance and does not mediate the relationship between financial characteristics and tax avoidance, suggesting that tax avoidance behavior is primarily driven by firms’ financial decisions rather than organizational maturity. These findings imply that regulatory attention should extend beyond tax reporting to corporate financing structures, as stronger monitoring of highly leveraged firms may enhance transparency and support sustainable public revenue systems. This study contributes by challenging the assumed mediating role of firm age and highlighting the context-dependent nature of leverage in shaping tax behavior in emerging markets, while also offering methodological robustness through the combined use of PLS-SEM and CB-SEM.