Bills may be initiated in the House or the Senate. Bills are assigned a legislative number, with H.R. for bills introduced in the House and S. for bills introduced in the Senate.
Each bill is referred to a committee and then usually to a subcommittee. After the subcommittee and committee is done holding hearings or revising the bill, the committee can report the legislation to the full chamber. Some bills simply die in committee.
In the full chamber of either the House or the Senate, after the debate and the approval of any amendments, the bill is passed or defeated by the members voting.
When the House or Senate passes a bill, it is referred to the other chamber, where it usually follows the same route through committee and floor action. This chamber may approve the bill as received, reject it, ignore it, or change it.
A conference committee made of House and Senate members can work out any differences between the House and Senate versions of the bill. The resulting bill returns to the House and Senate for final approval.
The Government Printing Office prints the revised bill in a process called enrolling.
After both the House and Senate have approved a bill in identical form, it is sent to the president. The President has 10 days to sign or veto the enrolled bill.
If the president vetoes the bill, it can still become a law if two-thirds of the Senate and two-thirds of the House then vote in favor of the bill.
Sources: U.S. House of Representatives & U.S. Senate