"The President's budget for FY2019 consists of a multivolume set of materials issued by the Office of Management and Budget (OMB). The materials contain information on new budget proposals, summary tables, detailed financial information on individual programs and accounts, economic analysis, historical data, explanations of the budget processes, and supporting documents. Every year the President submits these materials to Congress at the start of the budget cycle for the next fiscal year. The President's submission is required on or after the first Monday in January, but no later than the first Monday in February (31 U.S.C. §1105(a)). However, incoming presidential Administrations do not generally release multivolume budget sets in February. This year the President released the budget submission on February 12, 2018."
CRS Report for Congress, R43475