Eligibility
To naturalise as a British citizen you usually need to have lived in the UK for at least five years and held indefinite leave to remain or settled status for at least 12 months. If you are married to a British citizen you can apply as soon as you obtain settled status.
Applicants must be over 18, of sound mind and intend to continue living in the UK. You need to prove you were in the country exactly five years before your application date and you should not have spent more than 450 days outside the UK during that period, nor more than 90 days in the last 12 months. You must demonstrate knowledge of English, Welsh or Scottish Gaelic at B1 level and pass the Life in the UK Test. A good character requirement applies, meaning no serious criminal or immigration offences.