One Agency Act This bill consolidates federal antitrust enforcement authority in one department by transferring the Federal Trade Commission's (FTC) antitrust functions, employees, assets, and funding to the Department of Justice (DOJ). The bill provides a one-year period for DOJ to implement the transition and allows DOJ to extend the period once for an additional 180 days. During the transition period, DOJ may restructure the department's antitrust division and deputize FTC antitrust employees to investigate and prosecute antitrust violations on behalf of DOJ prior to the completion of the transfer of personnel from the FTC to DOJ. DOJ is also authorized to require businesses to file annual or special reports about the business’s organization, conduct, practices, management, and relationship to other businesses filing such reports.