Answer by alexg for Legal definition of a "criminal record"

In the united-kingdom there are basically three relevant levels of criminal record. The legislation is a little different between England and Wales, Scotland, and Northern Ireland. The official terminology in the Police Act 1997 is:

1. "Criminal conviction certificate"
2. "Criminal record certificate"
3. "Enhanced criminal record certificate"

A "DBS check" (Disclosure and Barring Service), or the equivalent in other UK jurisdictions for obtaining somebody's criminal record, will include one of these - DBS calls them "basic", "standard", and "enhanced".

These are distinct from "all the stuff that the police knows about you": any particular police force or similar agency might have all sorts of records about you. But they represent the three tiers of what other people are able to find out, from the police records. The level of information available is scoped for the reason that it's needed, e.g. somebody wanting a job working with children would need the highest level check.

In essence, the basic level shows convictions that are not "spent" (long enough ago that they do not need to be disclosed). The standard level shows convictions, cautions and warnings, even from long ago. The enhanced level can additionally include police information that they deem to be relevant, such as an arrest that did not lead to a conviction, or other reasons why the person has come to the police's attention. For convictions, the certificate shows the title of the offence (e.g. "theft"), date, and sentence, but no real detail (e.g. what was stolen).

An individual can obtain more information from their own police records by making a Subject Access Request under data protection law. But it's illegal for a prospective employer to say "show us the results of your SAR or else you're not getting the job" - they have to go through the appropriate DBS channel.

Exceptionally, there may be other kinds of disclosure for national security vetting or the like. And while you can still ask MI5 for a copy of their file on you, such a request is unlikely to be successful.