E. Mark Curtis and Ryan A. Decker | Entrepreneurship plays a vital role in the economy, yet there exists little well-identified research into the effects of taxes on startup activity. Using recently developed county-level data on startups, we examine the effect of states’ corporate, personal and sales tax rates on new firm activity and test for cross-border spillovers in response to these policies. We find that new firm employment is negatively–and disproportionately–affected by corporate tax rates. We find little evidence of an effect of personal and sales taxes on entrepreneurial outcomes. Our results are robust to changes in the tax base and other state-level policies.