We provide a randomized test of policy interventions that address barriers to naturalization for low-income immigrants. We find that offering fee vouchers doubles the naturalization application rate among low-income immigrants, but nudges often used by service providers did not increase applications among fee waiver-eligible immigrants below the poverty level. Our results help guide policy efforts to address the problem of low naturalization rates. The current high fees prevent a considerable share of low-income immigrants who desire to become Americans from submitting their applications. Lowering the fees should therefore increase naturalization rates and generate long-run benefits for new Americans and their communities. However, the poorest immigrants face deeper challenges to naturalization that are not easily overcome with the low-cost nudges we tested.