How does a bill become a law?

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

The first step is introduction. A member of the House or Senate introduces the bill in their chamber. Bills introduced in the House are assigned an H.R. number; bills introduced in the Senate are assigned an S. number. Revenue-raising bills must originate in the House.

The bill is referred to a standing committee 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 it to the full chamber. If the committee approves, the bill is reported to the floor. Most bills die in committee. The committee chair has substantial control over which bills are considered.

The full chamber debates the bill, may amend it further, and votes on final passage. The House operates under stricter rules and 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. After both chambers approve the same text, the bill is presented to the President. 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. If the President signs, the bill becomes law on the date of signature. 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. Congress can override a veto by securing a two-thirds majority in both the House and the Senate.

This 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.