Legislative process: taking a bill through Parliament

An overview of the process by which bills become law.

A bill is a proposed law which is introduced into Parliament. Once a bill has been debated and then approved by each House of Parliament, and has received Royal Assent, it becomes law and is known as an act.

Any Member of Parliament can introduce a bill. Some bills represent agreed government policy, and these are introduced into Parliament by ministers. Other bills are known as Private Members’ Bills.

This guide is about bills which affect the general law of the land. Special Parliamentary procedures apply to bills which apply only to particular people or places, and the government may have little or no involvement in this type of legislation.

Bills and acts are often referred to as primary legislation. An act may delegate power to a government minister to make regulations, orders or rules. These are known as secondary (or subordinate) legislation. Legislation can be found online at

The decision to legislate

For each session of Parliament the government will have a legislative programme, which is a plan of the bills that it will ask Parliament to consider in that session (the period between elections is divided up into sessions, and each of those sessions usually lasts about a year). Other bills may be passed each session that are not part of the legislative programme. These may for example be emergency bills required to deal with a particular issue that has arisen, or they may be Private Members’ Bills, introduced by a member who is not a part of the government.

If a government department has a proposal for a bill that it wants to be included in the legislative programme for a session, it must submit a bid for the bill to the Parliamentary Business and Legislation (PBL) Committee of the Cabinet. PBL Committee will consider all of the bids for that session and make a recommendation to Cabinet about the provisional content of the programme.

In considering whether to recommend that a bill should be given a provisional slot, PBL Committee will consider factors such as the need for the bill (and whether a similar outcome can be achieved by secondary legislation or without legislation), its relationship to the political priorities of the government, the progress that has been made in working up the proposals for the bill and whether the bill has been published in draft for consultation.

Once the provisional programme has been agreed by Cabinet, PBL Committee will review it in the lead-up to the beginning of the session. About a month before the start of the session the Cabinet will finalise the programme. This will be announced in the King’s Speech at the state opening of Parliament, which begins the session. The policy contained in the bill will also need agreement from the appropriate policy committee of the Cabinet.

Preparation of the bill

If a bill is given a slot in the legislative programme, the department concerned will create a bill team to co-ordinate its preparation and passage through Parliament. This will consist of a bill manager and other officials working on the bill. The other key players in the department will be the officials with lead responsibility for the policies in the bill and the department’s legal advisers.

The policy officials will prepare policy instructions for the departmental lawyers. These instructions will in turn form the basis of instructions to the Office of the Parliamentary Counsel to draft the bill. Instructions to counsel will set out the background and relevant current law and explain the changes in the law to be brought about by the bill. There will usually be at least two counsel assigned to the bill, and larger bills may well have more drafters. They will analyse the instructions and may have questions that need to be answered before drafting can begin. Once the drafters feel they have a clear idea of the policy, they will send drafts to the relevant departmental lawyers. The lawyers will discuss the drafts with the relevant policy officials and send comments back.

The first draft of a clause or set of clauses for a topic is rarely the final word on that topic, and the process of drafting and commenting on drafts will continue until the drafters and the department are happy that the right result has been achieved by the draft in the clearest possible way.

Some provisions in a bill may require input from departments other than the one sponsoring the bill. If the provisions of the bill apply to Wales or extend to Scotland or Northern Ireland, it may also be necessary for the department or the drafter to consult the devolved administration in the relevant part of the UK. Provisions in a bill which relate to matters that have been devolved to Senedd Cymru, the Scottish Parliament or the Northern Ireland Assembly will usually need the consent of that body.

Towards introduction

Although a bill may have a slot in the legislative programme, it cannot be introduced until it has been specifically cleared for introduction by a meeting of PBL Committee.

The committee will consider the final (or near-final) draft of the bill together with a range of other documents. Some of these, like the Explanatory Notes, will be published alongside the bill after introduction. Others, like the department’s Parliamentary Handling Strategy and its assessment of the relationship between the bill and the European Convention on Human Rights, are for the committee’s consideration only.

If PBL Committee is satisfied that the bill is ready and that other legal and procedural issues have been resolved, it will approve its introduction subject to any necessary minor and drafting changes. The committee may also decide whether the bill should start in the House of Commons or the House of Lords (see further below).

Some bills are published in draft for consultation before introduction. The bill may then go through a process of pre-legislative scrutiny where it is considered by a Parliamentary committee or committees. The committee will take evidence and make recommendations to the government on the bill. These recommendations, together with the consultation responses from members of the public, may mean that elements of the bill are modified before introduction. Publication of a bill in draft still needs the agreement of PBL Committee, although it will normally be cleared by correspondence rather than at a meeting.

Parliamentary Stages

Most bills can begin either in the House of Commons or in the House of Lords. The government will make this decision based on the need to make sure each House has a balanced programme of legislation to consider each session. However, certain bills must start in the Commons, such as a bill whose main aim is the imposition of taxation (the annual Finance bill is an example of this). Bills of major constitutional importance also conventionally start in the Commons.

Most bills will need to go through the following stages in each House before becoming law (what is said below applies to either House except where indicated).

First reading

This is a purely formal stage at which the title of the bill is read out. There is no debate on the bill.

Second reading

This is a debate on the main principles of the bill, held in the chamber. A government minister will open the debate by setting out the case for the bill and explaining its provisions. The opposition will respond and then other members are free to discuss it. The government will close the debate by responding to the points made. No amendments can be made to the text of the bill at this stage, although members may give an idea of the changes they will be proposing at later stages. At the end of the debate the House will vote on the bill. If the vote is lost by the government, the bill cannot proceed any further, though it is rare for a government bill to be defeated at this stage.

Committee stage

This is a line-by-line consideration of the detail of the bill. In the Commons this process may be carried out by a specially convened committee of MPs (a Public Bill Committee) that reflects the political composition of the House as a whole. Alternatively committee stage may be taken in the chamber (in which case it is called Committee of the Whole House). In the Lords the committee stage will take place in the chamber or a committee room in the Palace of Westminster; either way any peer can participate.

A Public Bill Committee in the Commons can take oral and written evidence on the bill. In either House the committee will decide whether each clause of the bill should remain in it, and will consider any amendments tabled by the government or other members.

The amendments tabled may propose changes to the existing provisions of the bill or may involve adding wholly new material. However, there are limits to what can be added to a particular bill, as the amendments must be sufficiently close to its subject matter when introduced.

Government amendments to bills (in committee or at other stages: see below) may be changes to make sure the bill works as intended, may give effect to new policy or may be concessionary amendments to ease the handling of the bill. Amendments in the last category will respond to points made at an earlier stage or will have been tabled to avoid a government defeat at the stage in question. Unless the amendments are purely technical in their effect, they will need the agreement of PBL Committee before they can be tabled, and substantial changes in policy will need policy clearance too.

Report stage

In both Houses this stage takes place in the chamber. Only amendments are discussed, so if none are tabled this will be a purely formal stage. As in committee the amendments may change what is in the bill already or may involve new provisions being added.

Report stage is also referred to as Consideration in the Commons.

Third reading

In the Commons this is another general discussion of the bill which invariably takes place immediately after report. No amendments are possible. In the Lords, third reading will take place on a later day, and tidying up amendments can be tabled.

Later stages

Both Houses must agree on the text of a bill before it can become an act. This means that if the bill is amended in the second House, it must return to the first House for those amendments to be considered. The first House can reject the amendments, make changes to them or suggest alternatives. A bill may move backwards and forwards between the two Houses a number of times before agreement is reached, so this stage is often called “ping pong”.

The time taken to go through all of these stages depends on the length of the bill, how controversial it is and whether it needs to be passed particularly quickly. An emergency bill may be passed in a matter of days, whereas a larger bill may be introduced at the beginning of the session and only passed at the end a year later.

Royal Assent and beyond

A bill that has been passed by both Houses becomes law once it has been given Royal Assent and this has been signified to Parliament. It will then become an act. Even then the act may not have any practical effect until later on. Most provisions in an act will either come into operation within a set period after Royal Assent (commonly two months later) or at a time fixed by the government. This gives the government and those people who are directly affected by the act time to plan accordingly. The government may need to fill in some of the details of the new scheme by making regulations or orders under powers contained in the act, for example to deal with procedural matters.

Three to five years after a bill has been passed, the department responsible for the act resulting from it should review how it has worked in practice and submit an assessment of this to the relevant Commons departmental committee. The committee will then decide whether it wants to carry out a fuller post-legislative enquiry into the act.

Published 20 February 2013
Last updated 14 March 2023 + show all updates
  1. Updated the core text to reflect the latest version.

  2. First published.