A bill becomes law through a step-by-step process that involves both chambers of Congress; that standard process is outlined here, though it is not followed in the case of all bills. The steps are identical in each chamber, with a few procedural exceptions. For example, appropriations bills—those that authorizes the government to spend money—can only be introduced in the House of Representatives.
The first step in the legislative process is sponsorship of the bill. A representative or senator—or a group of representatives or senators—may sponsor a bill for many reasons. Constituents in the legislator's home district or state may ask for specific legislation, or lobbyists and interest groups may have requested the bill. The president may have publicly pressed for the bill, which a congressional ally introduces. Or a legislator may initiate a bill on his or her own in order to address an issue important to that member or to a particular constituency. Often, representatives and senators work together to craft the bill and introduce it in both chambers. While the bill might begin with similar language, the process of debating and passing the bill in both chambers can result in the final version of the two bills being different.
Technically, any member can introduce a bill. However, the Speaker and Senate majority leader can make it clear to a member that they do not wish for the chamber to handle a particular bill and urge or pressure the member not to introduce it. The leaders typically apply such pressure for political reasons—for example, hoping to avoid a vote that would put members on record on a difficult issue that many of them want to avoid. This reason is particularly acute in an election year. The leaders may also discourage a bill they see as potentially problematic for a president of their own party.
Once submitted, the bill is given a number; House bills begin with the designation H.R. and Senate bills with an S. The bill is then assigned by the Speaker or the Senate majority leader to a congressional committee. The committee chair typically assigns a bill to all relevant subcommittees, which hold hearings to gather more information about the bill, often calling on experts from a related field. The subcommittees then markup on the bill. Markup is the process by which members of a congressional committee debate the merits and content of the bill, amending and rewriting it as necessary. Once the subcommittees send the bill back to the main committee, it completes markup. Then, either the bill is reported to the House or Senate as ready for consideration by that entire body, or it is tabled, meaning that it is no longer under consideration. Committees can block consideration of a measure by not reporting it to the full chamber. Both chambers allow the full body to prevent that blockage by passing a discharge petition, a procedure that forces a bill from the committee onto the chamber's floor for full debate and a vote.
The bill-writing process involving committees and subcommittees and including hearings is called regular order. Sometimes congressional leadership avoids this process to exercise closer control over the language of a bill deemed to be of high importance. In this case, the leaders of the majority party choose who will write the bill and work closely with them—and the White House if the president also comes from the majority party in Congress—to finalize the bill and introduce it to the floor for a vote.
When a bill is considered by the entire House, debate rules for that bill are determined by the Committee on Rules. The Speaker can influence the process here as well by working closely with the chair of the Rules Committee and the majority membership to issue rules that the Speaker wants. The Senate majority leader has less power over that chamber—Senate rules call for debate to be unlimited unless a majority votes to end debate. Once debate begins, amendments can be added if the rules established for the bill allow it. The House or Senate then votes on the bill, which passes if a simple majority votes in its favor. If the vote is tied in the Senate, the vice president can cast the deciding vote. The bill is then introduced in the other body of Congress, where it follows the same committee and debate process. If the bill also passes in the second body, it often does so in a different form. In such cases a conference committee may be formed to reconcile any differences between the versions of the bill passed by the House and the Senate, or the leadership of the two chambers may reconcile the bills.When the bill is deemed ready by the conference committee, it once again comes to a vote by both the House and the Senate. If it passes, the bill is then sent to the president for signature. The president can choose to sign the bill into law or veto it. A veto is the action by a president to reject legislation passed by Congress. If the president vetoes a piece of legislation, Congress has the option to override the veto, the action by Congress to pass a bill over a president's veto, which requires a two-thirds vote of both chambers. If the president does not take action on the bill within 10 days of receiving it, the bill becomes law. However, a president can carry out a pocket veto, the action in which a president refuses to sign a bill during the 10-day signing period while Congress is in adjournment. The fact that Congress is adjourned means that it cannot vote to uphold or override the veto.