What is an Act of Parliament?

An Act of Parliament is a law, known technically as a statute, that has been approved by both the House of Commons and the House of Lords and has received Royal Assent from the monarch.

Every Act begins life as a bill. Most are public bills brought forward by the government, but private members' bills introduced by backbench MPs or peers, private bills promoted by local authorities or companies, and hybrid bills that combine the two also follow the process. A bill passes through a defined series of stages in each House. In the Commons these are the first reading (a formal introduction), the second reading (a debate on the bill's principles), the committee stage (detailed line-by-line examination, usually in a Public Bill Committee), the report stage, and the third reading. The bill is then sent to the Lords, which follows a similar process. Any amendments made by one House must be accepted by the other before the bill can proceed. Disagreements between the Houses are resolved through a process known as "ping pong" in which the bill moves back and forth until agreement is reached.

Royal Assent is the final step. It has not been refused since Queen Anne declined the Scottish Militia Bill in 1708. In modern practice, Royal Assent is signified by the Speaker of each House rather than personally by the monarch. Once granted, the bill becomes an Act of Parliament, but the provisions do not always come into force immediately. Many Acts include commencement clauses or rely on commencement orders issued later by ministers, so the date of Royal Assent and the date on which the law takes effect can be years apart.

The Parliament Acts of 1911 and 1949 allow the Commons to pass legislation without the consent of the Lords in defined circumstances. Since 1949, this power has been used only to pass four Acts, including the War Crimes Act 1991 and the Hunting Act 2004.

Acts of Parliament are the principal form of primary legislation in the United Kingdom. Secondary legislation, usually in the form of statutory instruments, is made by ministers under powers granted in a parent Act and can be amended or revoked without the full legislative process. Notable Acts shaping modern British life include the Representation of the People Acts, the Race Relations Act 1976, the Human Rights Act 1998, and the Equality Act 2010.