Police registration certificate
Nationals of some countries that are coming to the UK for more than 6 months are required to register with the Police when they arrive in the UK. If you are making a visa application in the UK, and If you were required to register with the police when you arrived to the UK, you must submit your police registration certificate with your application.
After registration, it is important that you inform the police if you change your address, obtain a new visa or are issued with a new passport. You should make sure your certificate is up to date when you make your visa application.