Two routes, and which one you are on
Naturalisation comes in two forms and the difference is worth several years.
The general route. You must have been in the UK for at least five years, and have held indefinite leave to remain or settled status for at least twelve months before applying. That twelve-month wait is the part people forget: getting ILR does not mean you can apply the next day.
As the spouse or civil partner of a British citizen. You must have been in the UK for at least three years and hold ILR or settled status — but there is no twelve-month waiting period. You can apply as soon as you have settlement.
That second route is materially better and a great many people do not realise it applies to them. If you are married to a British citizen and have just received ILR, you may be able to apply for citizenship immediately rather than waiting a year.
Children are a different matter again. Rather than naturalising, they are usually registered as British citizens, and the requirements depend on how and when they were born and their parents' status. It is worth checking whether a child in your family is in fact already British — it happens more often than people think, particularly for children born in the UK who have lived here for ten years.
The residence calculation, exactly
This is arithmetic and it is where applications fail on technicalities.
On the five-year route you must not have been absent from the UK for more than 450 days in total across those five years, and no more than 90 days in the final twelve months.
On the three-year spouse route the limits are 270 days in total and, again, 90 days in the final twelve months.
You must also have been physically in the UK on the day exactly five years — or three years — before the Home Office receives your application. Not approximately. Exactly. A holiday on that date is a refusal, and it is the single most avoidable failure in this whole area.
There is discretion to overlook excess absences, but it is discretion and not entitlement, and it is exercised more readily where the reason was compelling and evidenced.
Work out the exact date before you do anything else. If it falls awkwardly, wait — an application submitted a fortnight later succeeds where one submitted on the wrong day does not.
Choosing your referees, properly
Every naturalisation application needs two referees, and the requirements are precise. Getting this wrong invalidates an otherwise perfect application, and it is one of the most common reasons for one to be returned.
Referee one must be a person of professional standing. That is a defined list and it is broader than people assume — it includes solicitors, accountants, doctors, dentists, teachers, engineers, police officers, ministers of religion, airline pilots, bank officers and civil servants, among others. They do not have to be British.
Referee two must be a British citizen aged 25 or over, holding a British passport.
Both referees must:
- Have known you for at least three years Personally, not professionally at arm's length. A doctor you have seen twice does not qualify simply by being a doctor.
- Not be related to you No family members, and that includes by marriage.
- Not be related to each other The two referees must be independent of one another.
- Not be your solicitor or agent We cannot act as your referee, and nor can anyone else representing you in the application.
- Not have a relevant criminal conviction An unspent conviction disqualifies a referee.
- Be aged 25 or over Applies to both, not only the British citizen referee.
Good character: further back than you think
The good character requirement is where applications fail on things people genuinely did not expect to matter.
Criminal history is the obvious one, and it includes cautions, fixed penalty notices in some circumstances, and matters you consider spent. Declare everything. An undeclared caution discovered later is treated as deception, and deception is far more damaging to a citizenship application than almost any underlying offence.
Immigration history counts. Overstaying, illegal working, breaches of conditions and previous deception all feed into it. Recent immigration breaches are generally a bar for a period of years.
Financial conduct is assessed too. Bankruptcy, unpaid debts to the Home Office or to HMRC, and failure to pay tax owed can all count against you. Unpaid NHS charges over a threshold are a specific and increasingly common problem.
Driving offences surprise people most. A pattern of them, or a serious one, can be enough on its own.
The practical advice is the same throughout: tell your solicitor everything at the first conversation, including things you are sure are irrelevant. Almost all of it can be dealt with properly if it is addressed in the application. Very little of it can be dealt with once the Home Office has found it themselves.
After approval: the ceremony
Approval is not the end. You must attend a citizenship ceremony within three months of receiving your invitation, where you swear an oath or make an affirmation of allegiance and pledge loyalty to the UK.
Ceremonies are arranged by your local council and there is a separate fee, usually included in the application fee. You become a British citizen at the ceremony, not when the letter arrives — which matters if you are planning travel, because you cannot apply for a British passport until afterwards.
One practical point worth planning for: if you need to travel urgently, arrange the ceremony before booking. Councils have limited slots and the three-month window is not generous.