British Citizenship-Birth in the United Kingdom
On 1 January 1983, the British Nationality Act 1981 came into force. One of the most significant changes implemented by the 1981 Act was to modify the law on British citizenship by birth in the United Kingdom (including, for nationality purposes, the Channel Islands and Isle of Man).
 "Settled in the United Kingdom"
This is defined in the Act as "ordinarily resident in the United Kingdom without limitation as to the time in which one can remain". "Ordinary residence" is a concept of "where is home, where is one living." And admission without limitation as to time, effectively "permanent residence", refers to any of the following:
 EU, EEA and Swiss citizens
Citizens of European Union and European Economic Area member nations (Switzerland is treated as EEA from 1 June 2002) may be treated as "permanent residents" for British nationality purposes, as follows:
 At the time of birth
In order for the U.K. born child to be British at birth automatically, one parent must be a British citizen or permanent resident at the time the child is born.
Many parents acquire permanent residence after the child is born. In this case, child may immediately be registered as a British citizen under section 1(3) of the British Nationality Act, provided application is made before age 18.
 Other options
 Child lives in the United Kingdom until age 10
A U.K. born child who lives in the United Kingdom until age 10 can be registered as a British citizen under section 1(4) of the British Nationality Act. There is no age limit to complete the registration, but it is subject to a "good character" requirement. It is also more difficult to evidence as time passes.
The immigration status of the child, or the parents, is irrelevant.
 British Overseas Territories
From 21 May 2002, a child born in most of the British Overseas Territories (with the exception of the special case of the Sovereign Base Areas of Cyprus) is treated as born in the United Kingdom for nationality purposes.
 Birth in Northern Ireland
Due to the law of the Republic of Ireland, every child born in Northern Ireland who is automatically a British citizen will also automatically be an Irish citizen, or "entitled to claim Irish citizenship" which amounts effectively to the same thing.
A child born in Northern Ireland may also be an Irish citizen, even if not a British citizen: