A British citizen by descent is a person born outside the United Kingdom who has acquired British citizenship because a parent was born or naturalised in the United Kingdom. It also includes certain persons who have acquired British citizenship by registration.
It does not include those who have migrated to the United Kingdom and become naturalised British citizens.
For nationality purposes, the "United Kingdom" includes the Channel Islands and Isle of Man.
Since 1983, as a general rule, if a person was born outside the United Kingdom to a parent in U.K. recruited "Crown Service" or designated equivalent, that person is deemed to have been born in the United Kingdom. For those born before 1983, it is more complex.
The fact that one is a British citizen by descent (or otherwise) is not generally shown on British passports. For that reason, it is necessary to provide more evidence when seeking proof of British citizenship for a child.
A person who is a British citizen by descent cannot "switch" to being a British citizen otherwise than by descent. However, there are mechanisms to deal with overseas born children of British citizens by descent where the British parent has close ties with the United Kingdom.
 Why make a distinction?
Since 1915, British nationality law has generally restricted the transmission of British citizenship beyond the first generation born overseas. It has been the view of successive British governments that those who leave the United Kingdom should generally "throw in their lot" with their adopted country. It is also the view that children born in another country will, if they are citizens of that country, generally identify more with that country as they grow up than the United Kingdom.
 British citizens by descent
The British Nationality Act 1981 specifically defines the categories of people who are British citizens by descent. Any British citizen not falling into one of these categories is a British citizen otherwise than by descent.
The following are the main categories of persons who are British citizens by descent:
Persons born since 1 January 1983
- Born outside the United Kingdom who automatically acquired British citizenship at birth.
- This does not apply to those born in a British Overseas Territory on or after 21 May 2002.
- Registered as a British citizen under the following sections of the British Nationality Act 1981:
- section 3(2) (parent a British citizen by descent who lived in Britain for 3 years)
- section 4B of the Act, since 30 April 2003 (British nationals with no other citizenship)
- section 4C of the Act, since 30 April 2003 (persons born before 1983 to a British mother, so-called "UKM" registration)
- Registered as a British citizen under section 3(1) of the 1981 Act, if a parent of the child was a British citizen when the child was born.
Persons born before 1 January 1983
- Born outside the "United Kingdom and Colonies" and automatically acquired U.K. citizenship at birth due to father being British born or naturalised.
- Born or naturalised in a colony with a parental or grand-parental link to the United Kingdom. (there may be exceptions if U.K. citizenship was lost at independence of a colony and then re-acquired).
- Registered as a Citizen of the U.K. & Colonies by a British High Commissioner in an independent Commonwealth country under section 7 of the British Nationality Act 1948 (children under 18), if the registration was done on or after 28 October 1971. (note that some in this category are British Overseas citizens, instead of British citizens).
- Women who acquired citizenship by registration under section 6(2) of the 1948 Act (wives of British men) to a man who became a British citizen by descent on 1 January 1983, or would have done if living.
- Persons born before 1949 who acquired U.K. citizenship under the 1948 Act under special provisions for those connected with the former Dominions (Australia, Canada, New Zealand, South Africa, plus Southern Rhodesia and the Republic of Ireland) who did not become citizens of these countries when they introduced a citizenship law.
- Note that the majority covered by these provisions became British Overseas citizens, but if British citizens they would usually be citizens by descent.
- Those who acquired British citizenship under the British Nationality (Hong Kong) Act 1997 are British citizens by descent if they had acquired British Dependent Territories citizenship by descent (broadly, those born outside Hong Kong)
- Spouses and children of those awarded British citizenship under the Hong Kong British Nationality Selection Scheme, under the British Nationality (Hong Kong) Act 1990, generally became British citizens by descent.
- Those who acquired British citizenship under special provisions dealing with statelessness (fairly unusual) are generally British citizens by descent.
 Consequences of being a British citizen by descent
If you are a British citizen by descent, you have the same rights as any other British citizen except that if you have a child born outside the United Kingdom (including the Channel Islands and Isle of Man), it will not automatically be a British citizen unless:
- the child is born in a British Overseas Territory (such as Bermuda), since 21 May 2002; or
- you are in U.K. recruited Crown Service, or designated equivalent; or
- the child acquires British citizenship from the other parent
 How can I get British citizenship for my child?
If your child is not automatically a British citizen, then there are [u]three[/u] options, usually, to get the child British citizenship:
Section 3(2) Registration
The child can be registered as a British citizen if:
- a parent is a British citizen by descent at the time of the child's birth; and
- the child has a grandparent who was a British citizen otherwise than by descent when the parent was born. (this effectively limits this kind of registration to the second generation born overseas); and
- the British parent has lived in the United Kingdom or a British Overseas Territory for a period of 3 years in which absences do not exceed 270 days, (this does not apply if the child has no other nationality at birth); and
- application is made while he is a minor (under no circumstances can this be extended). [See Clause 43, Borders Citizenship and Nationality Act 2009, effective from 13 January 2010. Prior to this date, the age limit was 12 months, extendable to 6 years in some cases.]
The child will, if registered, become a British citizen by descent.
Section 3(5) Registration
A child under 18 can be registered as a British citizen if:
- a parent is a British citizen by descent at the time of the child's birth; and
- the child, plus both parents (or one parent, if the parents are separated), has lived in the United Kingdom for at least 3 years immediately preceding the application.
- if aged 10 or over, child is of "good character".
The child will, if registered, become a British citizen otherwise than by descent. Effectively, the child must move to the U.K. by age 15 for this to be possible. Otherwise it will need to qualify for naturalisation as an adult.
Section 3(1) Registration
The Home Secretary has the power under the law to register any person under 18 as a British citizen. Obviously, the Home Office does not do this on a random basis and therefore policies have been developed to ensure this is done in a consistent manner.
Normally, if one parent is already a British citizen they look for:
- the child should be a permanent resident of the United Kingdom (holding Indefinite Leave to Remain, or equivalent); and
- the intention should be for the child to remain in the United Kingdom; and
- the child's other parent should be a permanent resident of the United Kingdom (unless the family has split up); and
- the child, if aged 10 or over, is of "good character"; and
- if the child is aged 13 or over, the child has lived in the United Kingdom for 2 years.
Registration under section 3(1) gives British citizenship by descent if one parent is a British citizen when the child was born. However, there may be exceptions, for example if the British parent became a British citizen after the child was born.
Section 3(1) registration is also used to deal with "special cases" not otherwise covered by the law, such as situations where a child of a British parent has no other nationality, or the special circumstances of British families on "long term business overseas". These cases are unusual.
In order to register a child as a British citizen:
- Form MN1 needs to be completed for each child with fee and supporting evidence.
- From April 2009, the fee will be GBP460. Additional children applying at the same time require a fee of GBP50 each (up to the fee change, a single fee of GBP400 covers multiple children).
- If child is outside the United Kingdom and the British territories, application needs to be submitted to a British diplomatic mission. They will forward the application to the Home Office for decision.
- A consular fee will be levied, in addition to the above fees (normally payable in local currency).
- Processing time for stand-alone child registrations is normally quite quick, no more than a few months in most cases.
- The Home Office will send the child's Certificate of Registration as a British citizen to the diplomatic mission, who will contact you.
- If child has turned 18 during processing, child will need to attend a citizenship ceremony.
With a Certificate of Registration, a child may apply for a British passport. This is not compulsory if there is no plan to move to the United Kingdom, however it is normally advisable.
 Immigration visa options
Normally, if you are a British parent you can bring your dependent child to the United Kingdom on a settlement visa so that the child can later be registered as a British citizen under section 3(1) or 3(5) of the Act.
If the child is older, he or she may qualify for an Ancestry Visa if there is a United Kingdom born grandparent and the child is a citizen of a Commonwealth country.
It would be unusual for Right of Abode to be an option, but it may be there for someone born before 1983 who:
- has a United Kingdom born mother; or
- was adopted by British parents; and
- has continuously been a citizen of a Commonwealth country since 1 January 1983.
 Proof of British citizenship
British citizenship may be proved by:
- a British passport; or
- if born in 1983 or later, a Certificate of Entitlement to Right of Abode stamped in a foreign passport; or
- if born in 1983 or later, a British consular birth certificate; or
- a nationality status letter issued by the Home Office.
- a Certificate of Registration issued by the Home Office (only if an application for British citizenship was required).
 Irish citizenship options
Many British citizens have, or are eligible for, citizenship of the Republic of Ireland. Under current law, Irish citizenship can be passed indefinitely down the generations provided the parent acquires Irish citizenship before the child is born. Irish citizenship by descent from an Ireland or Northern Ireland born parent is automatic, in other cases it is granted upon registration provided that the parent has become an Irish citizen before the child is born (special rules exist for those who registered as Irish citizens before 1987).
 Further information
Additional information can be found in the Home Office Nationality Instructions and Wikipedia (unofficial)