Visa holders and dependants (aged 16 or over) from some countries are required to register with the police and hold a Police Registration Certificate (PRC) if they are coming to the UK for longer than six months. Those required to register must report within 7 days after arriving in the UK, and then report certain changes to the police as they arise, keeping their PRC up to date.
It should be clearly stated in the Home Office letter confirming the visa application has been granted if a visa holder is required to register with the police.
If a visa holder is required to register with the police as part of their visa conditions but does not, they would be committing an offence, may have a fine imposed, and will encounter difficulties when they apply for a new visa.
The police registration requirement does not apply where a visa has been issued to come to the UK for less than six months. These requirements also do not apply to those who have been granted Indefinite Leave to Remain (ILR), as they are no longer subject to immigration restrictions.