What must happen for a bill to become law?

For a bill to become a law, both the U.S. House of Representatives and the U.S. Senate must pass it in identical form, and the President must sign it (or have a veto overridden by Congress). The full process is set out in Article I, Section 7 of the Constitution.

After a bill is introduced in either the House or the Senate, it is referred to one or more standing committees with jurisdiction over the subject matter. The committee may hold hearings, mark up the bill (consider and adopt amendments), and vote on whether to recommend the bill to the full chamber. Most bills die in committee without ever receiving a committee vote, let alone a full chamber vote. If the committee approves the bill, it is reported to the floor of the chamber.

The full chamber debates the bill, may amend it, and votes on final passage. The House operates under stricter rules and tighter time limits than the Senate; the Senate has the tradition of unlimited debate, which can lead to filibusters that require 60 votes for cloture before a final vote.

If the bill passes one chamber, it is sent to the other. The other chamber goes through the same process: committee referral, hearings, markup, floor debate, and vote. The other chamber may pass the bill as received, amend it, or reject it. When the chambers concur on a single version, the bill is enrolled and presented to the President for action. If the chambers pass different versions, a conference committee made up of members from both chambers may be appointed to resolve the differences. The conference report must then be approved by both chambers without amendment before going to the President.

The President has ten days (excluding Sundays) to act. The President's signature enacts the bill into law and assigns it a public-law number. The President can veto the bill, returning it to the originating chamber. If the President does neither, the bill becomes law after ten days if Congress is in session, or is killed by pocket veto if Congress adjourns. An override of the veto requires two-thirds in each of the two chambers of Congress.

The process is deliberately difficult. The framers wanted to ensure that legislation reflected broad agreement and was carefully considered. The result is that few of the thousands of bills introduced in each Congress actually become law.

Major legislation typically takes months or years to develop, with extensive negotiations among committee members, party leadership, the White House, and outside stakeholders. The complexity of the process means that even popular legislation can fail if proponents cannot navigate the procedural and political hurdles.