This paper investigates how firm-wide organizational competence shapes corporate tax outcomes. Exploiting China's Tax Compliance Rating (TCR) system, which evaluates the administrative execution of daily transaction flows across procurement, human resources, and supply chain operations, we examine whether operational rigor translates into superior tax performance. We document that top-tier (Grade A) firms achieve significantly lower effective tax rates. This association persists after controlling for general internal control quality, managerial ability, statutory tax incentives, auditor expertise, and state ownership. Importantly, this tax efficiency does not stem from aggressive or risky tax positions, as Grade A firms exhibit significantly lower tax volatility and no elevation in accounting or tax restatements. Dynamic tests further show that these tax advantages compound steadily with cumulative compliance experience. Overall, our findings demonstrate that corporate tax efficiency represents a tangible economic return on day-to-day administrative execution and cross-departmental coordination, establishing compliance ratings as a credible market signal of organizational competence.