Article 1 - The Legislative Branch
Section 7 - Revenue Bills, Legislative Process, Presidential Veto
All bills for raising Revenue shall originate in the House of Representatives; but the Senate may propose or concur with Amendments as on other Bills.
As our great leaders are good at doing they play games with the Constitution. In this case they take a bill that originates in the house, strip most everything out of it, pass the bill and then send it back to the house.