(This measure has not been amended since it was introduced. The summary of that version has been expanded because action occurred on the measure.) Thoroughly Investigating Retaliation Against Whistleblowers Act (Sec. 2) This bill amends the Whistleblower Protection Act of 1989 to reauthorize through FY2021 the Office of Special Counsel (OSC), an independent federal investigative and prosecutorial agency led by an official appointed by the President to protect federal employees, former employees, and applicants for employment from prohibited personnel practices (i.e., employment-related activities that violate the merit system through discrimination, retaliation, improper hiring practices, or failure to adhere to employment law). (Sec. 3) The OSC shall have access to any record or other information of any agency under its jurisdiction. The Department of Justice (DOJ) or an inspector general may withhold access to information if the disclosure could interfere with an ongoing criminal investigation or prosecution, but only if DOJ or the applicable agency head submits a report to the OSC describing the records withheld and the reasons for the withholding. (Sec. 4) The bill: (1) extends from 15 to 45 days the period for the OSC to review a disclosure of violations of law, gross mismanagement, or other matters; (2) requires an agency to provide a detailed explanation of any failure to take action to address information about a violation of law transmitted to it by the OSC; and (3) requires an agency to report to the OSC within 180 days on agency action proposed to address a violation of law, whether such proposed action has been taken, and if not, why not. (Sec. 5) The OSC may terminate an investigation of a prohibited personnel practice if: (1) it involves an allegation that has been previously made by the same person, (2) the OSC does not have jurisdiction to investigate such allegation, or (3) the person should have known of the alleged prohibited personnel practice earlier than three years before the OSC received the allegation. (Sec. 6) The bill expands the OSC's annual reporting requirements to include: (1) the cost of allegations disposed of by the OSC; (2) the number of stays or disciplinary actions that the OSC negotiates with agencies; (3) the number of corrective action petitions and disciplinary action complaints initiated before, and stays obtained from, the Merit Systems Protection Board; and (4) the number of prohibited personnel practice complaints that result in a favorable action or outcome for the complainant. The OSC must include in its publicly disclosed list of noncriminal matters referred to agencies: (1) any comments from the complainant, provided that the availability to the public is appropriate, not prohibited by law, and is consented to by the complainant; and (2) the OSC's comments or recommendations. (Sec. 7) The OSC shall design and establish a pilot program in FY2018-FY2019 to survey individuals who have filed a complaint or disclosure with the OSC. The responses shall be used to improve customer service at various stages of the review or investigative process. (Sec. 8) Penalties for violations of Hatch Act prohibitions against engaging in political activities may include a combination of the disciplinary actions and the civil penalty prescribed under current law. (Sec. 9) The OSC must prescribe and publish in the Federal Register any regulations necessary for the OSC to perform functions required by amendments made by this bill.