A bill is proposed legislation under consideration by a legislature. A bill does not become law until it is passed by the legislature and, in most cases, approved by the executive. Once a bill has been enacted into law, it is called an act of the legislature, or a statute. Bills are introduced in the legislature and are discussed, debated and voted upon.
The preparation of a bill may involve the production of a draft bill prior to the introduction of the bill into the legislature. In the United Kingdom, draft bills are frequently considered to be confidential. Pre-legislative scrutiny is a formal process carried out by a parliamentary committee on a draft bill. It is required in much of Scandinavia, occurs in Ireland at the discretion of the Oireachtas (parliament) and occurs in the UK at the government's discretion.
In the Parliament of Ireland under Poynings' Law (1494–1782) legislation had to be pre-approved by the Privy Council of Ireland and Privy Council of England, so in practice each bill was substantively debated as "heads of a bill", then submitted to the privy councils for approval, and finally formally introduced as a bill and rejected or passed unamended.
In the Westminster system, where the executive is drawn from the legislature and usually holds a majority in the lower house, most bills are introduced by the executive (government bill). In principle, the legislature meets to consider the demands of the executive, as set out in the Queen's Speech or Speech from the Throne.
Bills are generally considered through a number of readings. This refers to the historic practice of the clerical officers of the legislature reading the contents of a bill to the legislature. While the bill is no longer read, the motions on the bill still refer to this practice.
In the British/Westminster system, a bill is read the first time when it is introduced. This is accompanied by an order that the bill be printed and considered again. At the second reading the general merits of the bill are considered – it is out of order to criticise a bill at this stage for technical defects in drafting. After the second reading the bill is referred to a committee, which considers the bill line by line proposing amendments. The committee reports to the legislature, at which stage further amendments are proposed. Finally a third reading debate at which the bill as amended is considered in its entirety. In a bicameral legislature the process is repeated in the other house, before the Bill is submitted to the executive for approval.
Where a piece of primary legislation is termed an act, the process of a bill becoming law may be termed enactment. Once a bill is passed by the legislature, it may automatically become law, or it may need further approval, in which case enactment may be effected by the approver's signature or proclamation.
Bills passed by the legislature usually require the approval of the executive such as the monarch, president, or governor to become law. Exceptions are the Irish Free State from the abolition of the Governor-General in December 1936 to the creation of the office of President in December 1937, and Israel from its formation until today, during which period bills approved by the Oireachtas and Knesset respectively became/become law immediately (Though, in Israel's case, the laws are ceremonially signed after their passage by the President).
In some jurisdictions a bill passed by the legislature may also require approval by a constitutional court. If the court finds the bill would violate the constitution it may annul it or send it back to the legislature for correction. In Ireland, the President has discretion under Article 26 of the Constitution to refer bills to the Supreme Court. In Germany the Federal Constitutional Court has discretion to rule on bills.
In the United States, all bills originating in the House of Representatives begin with "H.R." and all bills originating from the Senate begin with an "S.". Every two years, at the start of odd-numbered years, the United States Congress recommences numbering from 1, though for bills the House has an order reserving the first 20 bill numbers and the Senate has similar measures for the first 10 bills. Joint resolutions also have the same effect as bills, and are titled as "H. J. Res." or "S. J. Res." depending on whether they originated in the House or Senate, respectively. This means that two different bills can have the same number. Each two-year span is called a congress, tracking the terms of Representatives elected in the nationwide biennial House of Representatives elections, and each congress is divided into year-long periods called sessions.
In the United Kingdom, for example, the Coroners and Justice Act in 2020 started as Bill 9 in the House of Commons. Then it became Bill 72 on consideration by the Committee, after that it became House of Lords Bill 33. Then it became House of Lords Bill 77, returned to the House of Commons as Bill 160 before finally being passed as Act no. 29. Parliament recommences numbering from one at the beginning of each session. This means that two different bills may have the same number. Sessions of parliament usually last a year. They begin with the State Opening of Parliament, and end with Prorogation.