Paycheck Security Act This bill modifies and increases the employee retention tax credit, allows a refundable payroll tax credit for the operating costs of employers, and provides a rebate in 2020 for certain small businesses and other business entities. The bill also authorizes additional appropriations to carry out the provisions of this bill and to provide for oversight by the Inspector General for Tax Administration of the Department of the Treasury. The Government Accountability Office must report on the effectiveness of the operative provisions of this bill.