Ballot Bills are a type of Private Members' Bill used in the House of Commons.
At the start of each new parliamentary year, backbench MPs are invited to enter their names into a ballot. The few MPs who are lucky in the draw may each bring in a Bill of their choosing, known as a Ballot Bill. Ballot Bills take priority over other Private Members' Bills when time is allocated for debates and so have a better chance of becoming law.
In the Lords, a Private Members' Bill ballot takes place at the start of a session to decide the order in which the first 25 Private Members' Bills will be introduced.