Why is registration with the police a mandatory requirement?

Migrants who are residing or working in the UK might be required to register with the police and obtain a Police Registration Certificate.

This is a mandatory requirement and the consequences can be serious for any foreign national failing to register. The list of nationals is found on Appendix 2 of the Immigration Rules. Please note that each time there is a change in personal circumstances, including inter alia a change of civil status, new address, passport's number or immigration status, the Police Registration Certificate must be amended accordingly.