A collar number, also known as a shoulder number, force identification number (FIN) or occasionally as force number, identifies police officers, police community support officers (PCSO), special constables and some police staff in UK police forces – other law enforcement agencies, such as HM Prison Service, have also adopted identification numbers. Although now displayed on epaulettes, it is still commonly referred to as a collar number. Although most forces issue a collar number to all warranted officers regardless of role, only uniformed officers of the ranks constable and sergeant actually display the numbers.