USPSTF Transparency and Accountability Act of 2013 - Amends the Public Health Service Act to expand the scope and responsibilities of the United States Preventive Services Task Force to require it to: (1) publish research plans to guide its systematic review of evidence and new science relating to the effectiveness of preventive services; (2) make available reports on such evidence and recommendations for public comment; (3) establish a system for grading preventive care products and services (Grades A, B, C, and D and a Grade I for insufficient information); and (4) convene a preventive services stakeholders board to advise it on developing, updating, publishing, and disseminating evidence-based recommendations on the use of clinical preventive services. Provides for the disclosure and management of conflicts of interest by members of the Task Force and the preventive services stakeholders board.

Directs the Government Accountability Office (GAO) to submit a report that: (1) lists current recommendations of the Task Force; (2) compares Task Force recommendations and recommendations of other federal health agencies, national medical professional societies, and patient and disease advocacy organizations; and (3) analyzes the impact of Task Force recommendations on public and private insurance coverage, access, and outcomes, including the impact of morbidity and mortality.

Amends title XVIII (Medicare) of the Social Security Act to eliminate the discretion of the Secretary of Health and Human Services (HHS) to deny payment for a Medicare preventive service that has not received an A, B, C, or I grade by the Task Force.