We examine the ACA’s target population of consumers who were uninsured before the law’s main coverage provisions took effect in 2014. In every state, tax returns were filed for 56% or more of those who now qualify for Medicaid and 84% or more of those eligible for health insurance tax credits. The minority of tax preparers who help their clients apply for health coverage have developed several effective models. States could test the impact of measures to increase tax preparation services’ contribution to enrollment while guarding against unethical or incompetent conduct. Federal policy could also play an important role.