Cost of Services and Translations Act or the COST Act This bill requires federal agency financial offices to include multilingual services accounting information in their mandatory annual reports to the agency head and to the Office of Management and Budget (OMB). The bill defines multilingual service to include (1) services provided by interpreters hired by an agency; (2) services resulting in additional expenses which an agency provides to assist its employees or contractors to learn a non-English language; (3) agency preparation, translation, printing, or recordation of materials in a language other than English; and (4) services provided or performed for the federal government by agency employees or contractors that require speaking a non-English language that result in wage differentials or benefits provided by the agency. The bill requires the annual financial management status report of the OMB to certain congressional committees to contain a Multilingual Services Expenses Report. The OMB shall issue guidance that an agency financial office must follow in compiling multilingual services accounting information.