overstaying in good character requirement - does it look at 5 years or 10 years of immigration history?

Overstaying
Where you are not disregarding immigration breaches relating to lawful residence, if a person has previously overstayed permission to enter or stay in the UK, it will normally be appropriate to refuse the application for citizenship, unless it is the sole adverse factor weighing against the person’s good character; and either:

the person’s application for leave to remain was made on or after 24 November 2016, and the application did not fall for refusal on the grounds of overstaying because an exception under paragraph 39E of the Immigration Rules applied
the period without leave was not the fault of the applicant, for example where it arose from a Home Office decision to refuse which is subsequently withdrawn or quashed or which the courts have required the Home Office to reconsider
For information on dealing with breaches of conditions see liability to administrative removal.

Prior to 28 June 2022, immigration breaches in the 5-year period before a citizenship application were normally a reason for refusal of citizenship on the grounds of not meeting the lawful residence requirement set out in section 4 and section 6 (read with paragraphs 1 and 2 of Schedule 1) of the British Nationality Act (BNA) 1981. If the breach was in the 10-year period before a citizenship application, it was normally grounds for refusal of citizenship on the basis of not meeting the good character requirement.

Schedule 1 of the Nationality and Borders Act 2022 (NABA 2022) amended the requirements for naturalisation and registration for British citizenship under sections, 6(1) and 6(2) of the BNA 1981, so that a person can be treated as meeting the lawful residence requirement during the qualifying period without further enquiry where they hold indefinite leave to enter or remain in the UK. This change commenced on 28 June 2022.

This change does not extend to applications to naturalise as a British overseas territory citizen.

To align with changes to the qualifying period, immigration breaches relating to lawful residence, other than illegal entry relating to applications made on or after 10 February 2025, may be disregarded when assessing good character where all of the following factors apply:

the person is applying for naturalisation as a British citizen, or registration as a British citizen under s.4(2), 6(1) or 6(2) of the BNA 1981 after 28 June 2022
that person holds indefinite leave to enter or remain (ILE or ILR, also known as settlement) in the UK
no concerns (for example, regarding the person’s character) have arisen since the grant of settlement which might cast doubt on the decision
Therefore, applications where it remains appropriate to consider immigration breaches relating to lawful residence, alongside other good character factors, may include but are not limited to:

where historic information has come to light which, had it been known at the time of granting settlement, may have led to refusal
where something occurred after the grant of settlement to indicate revocation of that status may be appropriate
applications to naturalise as a British overseas territory citizen
Immigration breaches that do not relate to lawful residence (for example working in breach of conditions, hiring illegal workers, or failure to observe reporting requirements) must still be considered.