British citizenship absences: the 450 and 90-day limits
To naturalise as a British citizen on the usual route, you can’t have been outside the UK for more than 450 days in the 5 years before you apply, or more than 90 days in the last 12 months — and you must have been in the UK on the first day of those 5 years.
British citizenship absences calculator
Only whole days away count: the days you leave and come back are days in the UK.
Trips out of the UK
The residence requirements
To naturalise on the usual route — with indefinite leave to remain, settled status or indefinite leave to enter for 12 months — you must have been:
- in the UK at the start of the 5 years ending with the date of your application;
- outside the UK for no more than 450 days in those 5 years;
- outside the UK for no more than 90 days in the 12 months ending with the date of your application.
If you’re married to, or the civil partner of, a British citizen, the period is 3 years and the limit is 270 days, with the same 90 in the last 12 months.
How the days away are counted
- Whole days only. The dates you leave and come back aren’t absences: leaving on 22 September and returning on 23 September counts as no absence.
- Fixed periods. Both periods end on the date of your application — they aren’t “any 5 years” or “any 12 months”, as the ILR rule is.
- The first day matters. You need to have been in the UK on the first day of the period, exactly 5 (or 3) years before your application is received.
Worked example
You were away from 1 February to 11 May 2026 — 100 whole days, all within the last 12 months if you apply in summer 2026. That’s over 90, so you’d wait: from 11 February 2027 the 12 months ending with your application hold 90 days away, and the 90-day limit is met (as long as the 5-year total stays at 450 or fewer).
ILR first, then citizenship
The ILR rule counts days away differently — at most 180 in any 12 months during your qualifying period. See the ILR absences calculator.
How FlySee counts it
FlySee doesn’t have a tracker for British citizenship yet: its UK settlement tracker counts the ILR rule. The calculator above counts as the Home Office guidance does — whole days away only, never the dates you leave and come back — over the 5 (or 3) years ending with the date you apply. It doesn’t know about absences the Home Office may disregard: those days are counted.