How about the Constitution!
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."
Article 1, Sec. 7[1]
Yes, that is what is written.
But Obama’s health care reform contains trillions of new fees and expenses and mandates for spending controls, and the bill that was passed originated in the Senate also. And nobody seems to care about that little “snafu” ....