To change the name on your passport or other official documents it would be necessary to execute a document known as a Deed Poll.
There is a misconception about the law regarding names. I regularly encounter people who think that the have both an “official” name and an ordinary name for everyday usage. For example many Catherines are called Kitty, Margarets are called Peg, and so on. The name by which a person wishes to be called is their name despite what it may say on the birth certificate or passport. However, if one wishes to change the name that is written on their passport or other official documents it would be necessary to execute a document known as a Deed Poll.
A Deed Poll is a document normally drawn up by a Solicitor which states that the person wishes to use the new name and discontinue using the old name. It is printed on special deed paper, signed and witnessed. This deed, together with the original birth certificate will be accepted for most administrative purposes. A witness also swears an affidavit stating that they properly witnessed the signing of the deed and the affidavit is kept with the Deed Poll.
Registration of Deed Poll
It is not a legal requirement to register the Deed Poll, however it is advisable to register, or enrol it in the Central Office of the High Court in Dublin. Registration does not give the Deed Poll any additional effect. The enrolment of the Deed Poll in the Central Office of the High Court is the only means of publicly recording the change of name. The registration has the effect of putting the entire population on notice that you have changed your name. It may also be a requirement of foreign authorities to see that the Deed Poll is properly registered, for example for a visa application.
The other advantage in registering the Deed Poll is that if the original document gets lost, the High Court will be able to furnish you with a certified copy. In practice, it is rare for a Deed Poll not to be registered.