This paper examines the noncustodial parent earned income tax credit (NCP EITC), a new type of credit recently enacted in New York and Washington, D.C. and proposed by Senator Bayh and then-Senator Obama in 2007. The NCP EITC offers an earned income tax credit to low-income noncustodial parents who work and pay their full child support. This paper describes the rationale for this policy and provides national estimates of the benefits and costs of an NCP EITC under three alternative policy scenarios. It also discusses several key design and implementation issues.