In parliamentary systems, approval of the executive is normally a formality since the head of state is directed by an executive controlled by the legislature. In constitutional monarchies, this approval is called royal assent. In rare cases, approval may be refused or "reserved" by the head of state's use of a reserve power. The legislature may have significantly less power to introduce bills on such issues and may require the approval beforehand. In Commonwealth realms the royal prerogative informs this. In the United Kingdom, for example, cases include payments to the royal family, succession to the throne, and the monarch's exercise of prerogative powers.