A bill is a proposal for a new law or a change to an existing law. The idea for a bill can come from a sitting member of the U.S. Senate or House of Representatives or be proposed during their election campaign. Bills can also be petitioned by people or citizen groups who recommend a new or amended law to a member of Congress that represents them.

Once a bill is introduced, it is assigned to a committee whose members will research, discuss, and make changes to the bill.

The bill is then put before that chamber to be voted on.

If the bill passes one body of Congress, it goes to the other body to go through a similar process of research, discussion, changes, and voting.

Once both bodies vote to accept a bill, they must work out any differences between the two versions. Then both chambers vote on the same version of the bill. If it passes, they present it to the president.

The president then considers the bill. The president can approve the bill and sign it into law. Or the president can refuse to approve a bill. This is called a veto.

If the president chooses to veto a bill, in most cases Congress can vote to override that veto and the bill becomes a law. But if the president does not sign off on a bill and it remains unsigned when Congress is no longer in session, the bill will be vetoed by default. This action is called a pocket veto, and it cannot be overridden by Congress.