Statutory instruments are made in a variety of forms, most commonly Orders in Council, regulations, rules and orders. The form to be adopted is usually set out in the enabling Act.
Statutory Instruments, also known as SIs, are a form of legislation which allow the provisions of an Act of Parliament to be subsequently brought into force or altered without Parliament having to pass a new Act. They are also referred to as secondary, delegated or subordinate legislation.
Acts of Parliament confer powers on Ministers to make more detailed orders, rules or regulations by means of statutory instruments. An Act will often contain a broad framework and statutory instruments are used to provide the necessary detail that would be too complex to include in the Act itself.
Statutory instruments can also be used to amend, update or enforce existing primary legislation.
The National Archives on behalf of HM Government maintain the full text of all published Statutory Instruments Legislation.gov.uk (external site) from 1987.