A prerogative instrument is a legal instrument

Legal instrument

Legal instrument is a legal term of art that is used for any formally executed written document that can be formally attributed to its author, records and formally expresses a legally enforceable act, process, or contractual duty, obligation, or right, and therefore evidences that act, process, or...

 issued in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 under the royal prerogative

Royal Prerogative

The royal prerogative is a body of customary authority, privilege, and immunity, recognized in common law and, sometimes, in civil law jurisdictions possessing a monarchy as belonging to the sovereign alone. It is the means by which some of the executive powers of government, possessed by and...

, in contrast with a Statutory Instrument

Statutory Instrument

A Statutory Instrument is the principal form in which delegated or secondary legislation is made in Great Britain.Statutory Instruments are governed by the Statutory Instruments Act 1946. They replaced Statutory Rules and Orders, made under the Rules Publication Act 1893, in 1948.Most delegated...

 (which is made under the authority of an Act of Parliament

Act of Parliament

An Act of Parliament is a statute enacted as primary legislation by a national or sub-national parliament. In the Republic of Ireland the term Act of the Oireachtas is used, and in the United States the term Act of Congress is used.In Commonwealth countries, the term is used both in a narrow...

).

Examples of prerogative instruments include letters patent

Letters patent

Letters patent are a type of legal instrument in the form of a published written order issued by a monarch or president, generally granting an office, right, monopoly, title, or status to a person or corporation...

 (including most royal charter

Royal Charter

A royal charter is a formal document issued by a monarch as letters patent, granting a right or power to an individual or a body corporate. They were, and are still, used to establish significant organizations such as cities or universities. Charters should be distinguished from warrants and...

s), royal instructions

Royal instructions

Royal instructions are formal instructions issued to Governors of the United Kingdom's colonial dependencies. They have also been issued to the Governor General of certain Commonwealth realms.Traditionally the royal instructions were issued to a Governor to:...

, royal warrant

Royal Warrant

Royal warrants of appointment have been issued for centuries to those who supply goods or services to a royal court or certain royal personages. The warrant enables the supplier to advertise the fact that they supply to the royal family, so lending prestige to the supplier...

s, and some orders in council.

The use of prerogative instruments has declined considerably both as a result of the transfer of political power from the Sovereign to the House of Commons

British House of Commons

The House of Commons is the lower house of the Parliament of the United Kingdom, which also comprises the Sovereign and the House of Lords . Both Commons and Lords meet in the Palace of Westminster. The Commons is a democratically elected body, consisting of 650 members , who are known as Members...

, and with the expanded use since the nineteenth century of delegated legislation

Delegated legislation

In the United Kingdom, delegated legislation is legislation or law that is passed otherwise than in an Act of Parliament . Instead, an enabling Act confers a power to make delegated legislation on a Government Minister or another person or body...

under the authority of parliament.

Prerogative instruments were often used as the basis for the constitutions of British colonies.