The Constitution establishes that the legislative function is exercised collectively by the two Chambers (Article 70). This means that to become law a project must be approved in the same text by the House and the Senate. The procedure for the formation of the law (the so-called iter) is therefore divided into successive phases:
the presentation of the bill (legislative initiative)
the approval of the Chamber to which it was first presented
the transmission of the text to the other Chamber and its approval in the same formulation or with modifications: if it is modified, the project passes from one Chamber to the other, until it is approved by both in the identical formulation (it is the so-called shuttle)
its publication in the Official Gazette and its entry into force. In the Chamber, the main steps in the ordinary procedure are the following:
a bill, consisting of one or more articles and preceded by an illustrative report, can be presented by the Government, by each deputy, by at least 50,000 voters (these are popular initiative laws), by the National Council of Economy and labor or regional councils. In the Chamber, the texts presented by the Government are defined as bills, while all the others are referred to as bills;
The draft law is first assigned to the parliamentary commission responsible for the matter, which carries out an investigation, prepares a text to be submitted to the Assembly and presents a report .
In its preliminary activity, the Commission may decide to treat together two or more projects (which are called combined ) to present a single report and a single text to the Assembly. To this end, it can choose one of the projects as the basic text of the discussion or it can proceed – possibly appointing a select committee – to drafting a unified text of the various projects.