A bill is introduced by a sponsor(s) in one or both houses of Congress. A bill is assigned a bill number (H.R. 14, 107th Cong., 1st Sess. (2001)). This bill number usually follows the proposed legislation through hearings, amendments, congressional committees, etc., until enactment or the end of the current legislative period. A companion bill may be introduced in the other house of the legislature at any time.
When both houses pass the bill in identical form, it is sent to the president for a signature or veto.