In parliamentary procedure, cloture (pr: KLO-cher) (also called closure) is a motion or process aimed at bringing debate to a quick end.

The procedure originated in the French National Assembly, from which the name (originally clôture) in French is taken. It was introduced into the United Kingdom Parliament by William Gladstone to overcome the obstruction of the Irish nationalist party and was made permanent in 1887. It was subsequently adopted by the United States Senate and other legislatures.

United Kingdom

A motion for closure may be adopted in both the House of Commons and in the House of Lords by a simple majority, or more than one-half, of those voting. In the House of Commons at least one hundred Members must vote in favour of the motion for closure to be adopted; the Speaker of the House of Commons may choose to deny the closure motion if he feels that insufficient debate has occurred, or that the procedure is being used to violate the rights of the minority. In the House of Lords, the Lord Chancellor does not possess an equivalent power. Closure motions are often referred to as "guillotines".

United States

A similar procedure was adopted in the United States Senate in 1917 in response to the actions of isolationist senators who attempted to talk out, or filibuster, a bill to arm U.S. merchant ships. President Woodrow Wilson urged the Senate to change its rules to thwart what he called a "little group of willful men", to which the Senate responded by introducing cloture in the form of Rule 22.

This originally required a supermajority of two-thirds of all senators (i.e. 67 out of 100). However, it proved very difficult to achieve this; the Senate tried eleven times between 1927 and 1962 to invoke cloture but failed each time. It was particularly heavily used by senators from Southern states to block civil rights legislation. In 1975, the supermajority was reduced to three-fifths (60 out of 100). Some senators wanted to reduce it to a simple majority (51 out of 100) but this was rejected, as it would greatly diminish the ability of the minority to check the majority.

The procedure for "invoking cloture," or ending a filibuster, is as follows:

• A minimum of sixteen senators must sign a petition for cloture.
• The petition may be presented by interrupting another Senator's speech.
• The clerk reads the petition.
• The cloture petition is ignored for one full day during which the Senate is sitting (If the petition is filed on a Friday, it is ignored until Tuesday, assuming that the Senate did not sit on Saturday or Sunday.)
• On the second calendar day during which the Senate sits after the presentation of the petition, after the Senate has been sitting for one hour, a "quorum call" is undertaken to ensure that a majority of the Senators are present.
• The President or President pro tempore presents the petition.
• The Senate votes on the petition; three-fifths of the whole number of Senators (sixty with no vacancies) is the required majority; however, when cloture is invoked on a question of changing the rules of the Senate, two-thirds of the Senators voting (not necessarily two-thirds of all Senators) is the requisite majority.

After cloture has been invoked, the following restrictions apply:

• No more than thirty hours of debate may occur.
• No Senator may speak for more than one hour.
• No amendments may be moved unless they were filed on the day in between the presentation of the petition and the actual cloture vote.
• All amendments must be relevant to the debate.
• Certain debates on procedure are not permissible.
• The presiding officer gains additional power in controlling debate.
• No other matters may be considered until the question upon which cloture was invoked is disposed of.

Cloture does not automatically stop all delaying tactics, as it still permits up to 100 hours to debate any amendment made to a bill. This has led to opponents loading a bill up with amendments before cloture, a tactic devised by the late Senator James Allen.