Tax bills and all other bills that generate income for the country originate in the House of Representatives. The Senate can propose amendments to increase, decrease or otherwise change tax bills. Once a tax bill passes the House of Representatives, it must pass the Senate and be approved by the president before becoming law.
If the president approves and signs a bill, it becomes law. If the president rejects the bill or proposes changes, called Objections, the bill is sent back to the House of Representatives. The House of Representatives has to reconsider the bill with the Objections. If the bill passes the House with a two-thirds majority vote, the bill and the Objections are sent to the Senate for approval. If two-thirds of the Senate approve the bill, it then becomes law. If the tax bill fails at any step, it is dismissed. The bill also has to be returned to the president within 10 days, excluding Sundays, to be entered into law. Otherwise, the bill does not become law and is dismissed; this is the so-called pocket veto, a veto by way of doing nothing with the bill. The president can use a veto on the initial bill to force the two houses of Congress to compromise on its content.