The British Nationality Act 1981 confers two ways of naturalisation as a British citizen:
Section 6(1)
If, on an application for naturalisation as a British citizen made by a person of full age and capacity, the Secretary of State is satisfied that the applicant fulfils the requirements of Schedule 1 for naturalisation as such a citizen under this subsection, he may, if he thinks fit, grant to him a certificate of naturalisation as such a citizen.
Section 6(2)
If, on an application for naturalisation as a British citizen made by a person of full age and capacity who on the date of the application is married to a British citizen, or is the civil partner of a British citizen, the Secretary of State is satisfied that the applicant fulfils the requirements of Schedule 1 for naturalisation as such a citizen under this subsection, he may, if he thinks fit, grant to him a certificate of naturalisation as such a citizen.
The difference between these routes is based on whether you are naturalising on the basis of your marriage to a British citizen. Section 6(1) applies if you are not married to a British citizen and Section 6(2) applies if you are. The residence requirements must be met for both routes.
Residence Requirements
If applying under Section 6(1), the applicant must have:
Been in the UK at the beginning of the 5 year period before the date of application
Not been absent from the UK for more than 450 days in that 5 year period and 90 days in the 12 months before the date of application
If applying under Section 6(2), the applicant must have:
Been in the UK at the beginning of the 3 year period before the date of application
Not been absent from the UK for more than 270 days in that 3 year period and 90 days in the 12 months before the date of application.
Both Sections 6(1) and 6(2) also require the applicant to not have been in breach of immigration laws at any time within the 5 or 3 year period before the date of application.
The Qualifying Period
The 5 or 3 year qualifying period is calculated using the date of application for naturalisation minus the length of the qualifying period. For example, an applicant applying under Section 6(1) who made an application on 1st March 2023 must have been legally present in the UK on 1st March 2018. Similarly, an applicant applying under Section 6(2) who applied on 1st March 2023 would have to show they were legally present in the UK on 1st March 2020.
What If the applicant was not present?
If the applicant was not legally present in the UK at the start of the qualifying period, the applications will normally be refused. However, there are few limited situations where UKVI may exercise discretion, as introduced by The Nationality and Borders Act 2022.
Incorrect Removal
Where the applicant was prevented from being in the UK because they were removed, but the decision to remove them was later overturned.
Incorrect Prevention of Return
Where the applicant was incorrectly prevented from resuming permanent residence in the UK following an absence. For example, where the applicant held Indefinite Leave to Remain but was incorrectly considered to have been absent from the UK for more than 2 continuous years, and thereby losing their ILR status.
Exceptional Reasons Preventing Travel
Where the applicant was normally resident in the UK but there were exceptional reasons why they could not return from abroad at that time. For example, due to illness or travel restrictions because of the pandemic.
Member of Armed Forces
Where the applicant is a current or former member of the armed forces who was a member of the UK armed forces on the first day of the 5 year qualifying period and they were unable to be physically present on the first day due to their service in the armed forces.
What if the Qualifying Period has been miscalculated?
Applicants are asked on the application form to agree that UKVI use a different date as the date of application where this would work to their advantage. For example, if an applicant did not satisfy the requirements of the qualifying period at the date of application but does meet them at any time between the date of application and the date the application is considered, the application may be granted. If the qualifying period would be satisfied within 2 months of the date of consideration, UKVI may put the application on hold until the qualifying period is met. If the qualifying period is over 2 months away, the application will likely be refused unless there are exceptional reasons to exercise discretion.