they are aged 18 or over
they are of a 'sound mind' - in other words, they can make independent decisions (or appoint someone who can do so on their behalf)
they are of good character
they intend to continue living in the UK
they have the ability to communicate in English, Welsh or Scottish Gaelic
they have passed the 'Life in the UK' test or completed an English for Speakers of Other Languages (ESOL) course in addition to citizenship classes. The Life in the UK test includes questions about British traditions and customs as well as proving that the applicant can speak English
they must have lived in the UK for a minimum of five years before the date on which the application was made (unless their spouse or civil partner is a British citizen). They must have spent a maximum of 450 days outside the UK during those five years and no more than 90 days outside the UK in the previous 12 months. This excludes time spent as a diplomat or member of the armed forces, which are exempt from immigration control
they must have been granted indefinite leave to remain in the UK - that is, there is no date on which they have to leave the country
they must have had indefinite leave to remain in the UK for the previous 12 months (unless their spouse or civil partner is a British citizen)
they must have abided by the immigration laws while resident in the UK.