This article examines efforts to increase taxation of highly concentrated, undertapped income and profits in Latin America in the aftermath of structural adjustment. Argentina has advanced further than Chile in two policy areas: corporate taxation, which taps firm-level profits; and tax agency access to bank information, which helps reduce income tax evasion. These outcomes are explained by drawing on the classic concepts of business instrumental power, which entails political actions, and structural power, which arises from investment decisions. In Chile, strong instrumental power removed reforms in both areas from the policy agenda. In Argentina, much weaker instrumental power at the cross-sectoral level facilitated corporate tax increases. Bank information access was expanded after Argentina's 2001 crisis weakened the financial sector's instrumental power and reduced structural power.