A bill may originate in either the House or the Senate, and the procedure is almost identical. Each bill must be read by title on three different days in each chamber before it is passed. The first reading introduces the bill, and the second reading allows for amendments. When a bill is called for its third reading, it is voted on.
When the Senate does not amend an original House bill, it goes to the Governor for final action. The Governor may sign the bill, allow it to become law without his signature, or veto it.
If the Senate amends the bill, it goes back to the House. If the House concurs with the Senate amendments, the bill goes to the Governor. However, the House may refuse to accept the Senate amendments. If the Senate withdraws its amendments, the bill goes to the Governor. If the Senate does not withdraw its amendments, the bill goes to conference committee where differences may be worked out. If agreement is reached by both chambers, the bill goes to the Governor.
If the amended bill is rejected by the House, and either the House or the Senate fails to approve the first conference committee report, the bill may go to a second conference committee. If either the House or the Senate does not approve the second conference committee report, the bill is dead.
Source: Illinois Handbook of Government, p. 16.