The President of the United States has 10 days, excluding Sundays, to sign a bill from the day Congress passes it. If the President does not sign the bill, it does not become law, and the action becomes a pocket veto.
The veto power of the U.S. President means that he can return a bill to the House of Senate, where it originated, with explanations for the reasons of overturning. The chamber can attempt to override the President's veto, but this requires a vote of two-thirds of present members of the House. Once the President signs a bill, it becomes a law with an assigned number.