An individual is tax resident for a particular tax year if present in Ireland for 183 days or more in that year, or 280 days or more in that and the preceding year combined, including at least 30 days in each year. An individual is resident in Ireland for a day if present for any part of the day.
There are also specific tax rules in relation to split year relief which may have relevance to individuals arriving in or departing from Ireland.
Ordinary residence is specifically defined under Irish tax law. An individual obtains ordinary residence after a continuous period of tax residence and generally lasts for a period after normal tax residence has ceased. Ordinary residence begins after an individual has been tax resident in Ireland for three consecutive years (i.e. at the beginning of the fourth year). Ordinary residence ceases when the individual has been a non-tax resident for three consecutive years.
Domicile is essentially the country which is considered to be one’s permanent home, and is distinct from legal nationality and residence.