You mean you have a criminal record and you want to get rid of it? In the UK you have to declare any convictions you have for 7 years after the date of conviction, after which time they become 'spent'. However any convictions you have stay on your police record for 20 years, although you do not have to declare them unless you work with vulnerable people (ie in a school, hospital, etc). After this 20-year period is up, you can request that your records are destroyed, which you are entitled to witness