How a bill becomes law
The nutshell
A bill is a plan for a new law. Before a bill becomes law, it must be agreed by the House of Commons and the House of Lords and then approved by the King.
Every fact on this page comes from official Parliament guides and non-partisan explainers. Each source tag — like Parl — opens where a fact comes from.
The basics
What a bill is
A bill is a plan for a new law. A bill is not law yet — it is only a draft that Parliament looks at. Most bills are put forward by the government, but any MP can put one forward. A bill becomes an Act of Parliament, a real law, only after passing every stage.HoC
The stages in each House
In each House, a bill goes through five main stages. The first reading just introduces the bill, with no debate. The second reading is the first big debate on the whole idea. At committee stage, a small group of MPs checks the bill line by line and can suggest changes, called amendments. The report stage looks at those changes, and the third reading is the final vote in that House.IfG
Both Houses must agree
A bill must pass these stages in the House of Commons and in the House of Lords. Both Houses must agree the exact same words. If one House changes the bill, it goes back to the other House to look again. A bill can pass back and forth a few times until both Houses agree. This back-and-forth has a nickname: ping pong.GOV
The last step: Royal Assent
After both Houses agree, one step is left. The bill goes to the King for Royal Assent. Royal Assent is when the monarch formally agrees to make the bill a law. The moment Royal Assent is given, the bill becomes an Act of Parliament.Parl
- A bill can start in either the House of Commons or the House of Lords, according to UK Parliament
- Most bills that become law are put forward by the government, the Institute for Government notes
- Royal Assent, the King's approval, is now a formality and has not been refused since 1708, UK Parliament records
- A bill is only a plan and is not law until it has passed every stage, the House of Commons Library notes
- Both the Commons and the Lords must agree the same text, so the Lords cannot be skipped, GOV.UK explains
- Winning one vote is not enough, because a bill has three readings plus committee and report stages in each House, the Institute for Government sets out
The deep end6 min
From idea to bill
Before a bill reaches Parliament, an idea for a law is often worked on inside government. The Institute for Government notes that a draft bill is sometimes checked first in a step called pre-legislative scrutiny, where a committee of MPs and peers takes evidence and examines the text.IfG A peer is a member of the House of Lords. Not every bill gets this early check.
The five stages, in full
Once introduced, a public bill takes five steps in each House: first reading, second reading, committee stage, report stage and third reading, according to the Institute for Government.IfG The first reading is a formal start with no debate. The second reading is a debate and vote on the main idea. Committee stage is the close, line-by-line check, where amendments are proposed. Report stage reviews those amendments for the whole House. The third reading is the last debate and vote before the bill moves to the other House.
Agreeing the text: ping pong
A bill becomes an Act only when the House of Commons and the House of Lords agree exactly the same text, the House of Commons Library records.HoCIf the second House amends the bill, GOV.UK explains that it returns to the first House, and a bill can move between the two Houses several times before both agree, a stage nicknamed ping pong.GOV
Royal Assent, and what happens next
Once both Houses agree, the bill is sent to the monarch for Royal Assent, the formal step that turns it into an Act, UK Parliament states.ParlUK Parliament records that Royal Assent has not been refused since 1708, when Queen Anne blocked a bill on the Scottish militia, so the step is now a formality.Parl An Act does not always take effect at once. GOV.UK notes that many Acts come into force weeks or months after Royal Assent, on a date set by the government.GOV