From the Gov.UK website.
In addition to an identity check, the three main ways in which your personal information will be processed are:
- criminality and security checks;
- if you have provided your National Insurance number, real time checks with the Department for Work and Pensions and HM Revenue and Customs to consider evidence of your residence in the UK (for example tax or benefit records); and
- on a case by case basis, sharing information with other organisations to verify evidence you have provided within your application to protect against fraud and the use of counterfeit documents (for example verifying with a university that the university certificate you have provided is genuine)
This data sharing is designed to help applicants evidence their status in a quick and straightforward way by using data already held by other Government departments.
If the data is already held the checks would take minutes.