The following are the requirements to qualify for ILR Visa UK :

The applicant needs to have had an indefinite leave to remain in the UK for atleast 10 years.
They need to be of pensionable age and have made National Insurance contributions for at least one year.
They must also be living in the UK ,unless they are a refugee or a person with humanitarian protection.
They must not be an illegal immigrant , someone who has been given leave as a result of their marriage or civil partnership or someone who has been given leave as a result of their work status.

The applicants needs to submit a form which includes their name and date of birth along with proof that they have met all the requirements listed above.