A person who has continuously remained the UK under one or more visa category for a period lasting 10 year or over will be eligible to apply for Indefinite Leave to Remain in the United Kingdom.

A person who has had at least 14 years continuous residence in the United Kingdom, excluding any period spent in the United Kingdom following illegal stay or service of notice of liability to removal or notice of a decision to remove by way of directions may also be eligible to apply for indefinite leave to remain in the United Kingdom,

Continuous stay in the UK

Long residence in the United Kingdom means residence in the United Kingdom for an unbroken period with an unbroken absent for a period lasting 6 months at any one time, unless the applicant has limited leave to enter or remain upon their departure and return, "lawful residence" means residence which is continuous residence with existing leave to enter or remain in the UK.

Requirements

You must not have spent a total of more than 18 months absent from the United Kingdom during the long residence in the UK
You must demonstrate public interest there are no reasons why it would be undesirable for you to be given indefinite leave to remain on the ground of long residence with regards to your age, strength of connections in the UK, and personal history, including character, conduct, associations and employment record; domestic circumstances; and previous criminal record and the nature of any offence of which the person has been convicted; and compassionate circumstances; and any representations received on the person’s behalf

Further Information

An applicant granted indefinite leave has no restriction to employment
An applicant who has indefinite leave to remain can have his dependants join him
An applicant who has indefinite leave can apply for British Naturalization to become a British Citizen after a period of 1 year spent on Indefinite leave, and who has also remained in the UK for a total period of 5 years and 3 years under marriage
An applicant who has indefinite leave must not continuously remain outside the United Kingdom for a period 2 years, as the applicant’s leave may be curtailed if there is no good reason for that period absence