Using Census microdata on multi-state firms, we estimate the impact of state taxes on business activity. For C corporations, employment and the number of establishments have corporate tax elasticities of -0.4, and do not vary with changes in personal tax rates. Pass-through entity activities show tax elasticities of -0.2 to -0.3 with respect to personal tax rates, and are invariant with respect to corporate tax rates. Reallocation of productive resources to other states drives around half the e¤ect. Capital shows similar patterns but is 36% less elastic than labor. The responses are strongest for firms in tradable and footloose industries.