Portable Benefits for Independent Workers Pilot Program Act This bill requires the Department of Labor to award grants for FY2020, on a competitive basis, to states, local governments, or nonprofit organizations to support broad innovation and experimentation with respect to portable benefits. Portable benefits are work-related benefits that are provided to workers who are not traditional full-time employees in a manner that allows the worker to maintain the benefits upon changing jobs. The grants must be used for (1) the evaluation, or improvement to the design or implementation, of existing models or approaches for providing portable benefits; or (2) the design, implementation, and evaluation of new models or approaches for providing such benefits. The grants may not be used for a model or approach that provides only retirement-related benefits. The Government Accountability Office must evaluate and report to Congress on the outcome of the grants awarded pursuant to this bill.