Double Taxation Relief Manual: Guidance by country: Ireland: Nationals
Article 3(l)(c) defines `nationals’ of each country. An individual’s nationality (United Kingdom or Irish) normally only needs to be considered in deciding which country has primary taxing rights over government remuneration and pensions (Article 18 and see DT9890). The following notes refer to individuals only.
An Irish national is defined as a citizen of Ireland. A citizen of Ireland is an individual who was born in Ireland (under the Irish Constitution, Ireland includes the whole island, its islands and the territorial seas), or if his father or mother was an Irish citizen at the time of his birth or would have been if alive at the passing of the Irish Nationality and Citizenship Act 1956. However, an individual born in Northern Ireland on or after 6 December 1922 is not an Irish Citizen unless he makes a declaration in the prescribed form that he is an Irish citizen or, if a minor, his parent or guardian declares him to be an Irish citizen.
United Kingdom national
A United Kingdom national is defined as, amongst other things, a citizen of the United Kingdom and colonies and a British subject under Section 2, British Nationality Act 1948. A person born before 1 January 1949 was a British subject at birth if he or his father had been born in that part of Ireland now forming the Republic of Ireland. Such an individual lost his status as a British subject on 1 January 1949 unless he gave notice under Section 2 of the British Nationality Act claiming to retain British nationality. For the purpose of the agreement, such an individual is not regarded as a British subject unless his notice under Section 2 was acknowledged before 2 June 1976.
It will be seen, therefore, that individuals could well have both United Kingdom and Irish nationality simultaneously.