The address has to name the county
The listing states it flatly: the names of the county and the delivery office must form part of the address of all mail articles. Not the postal code, not the town alone. This is the single most common defect in an American-written Irish address, because a domestic habit of city plus ZIP does not carry over.
Carlow, Cavan, Clare, Cork, Donegal, Dublin, Galway, Kerry, Kildare, Kilkenny, Leitrim, Laioghis, Limerick, Longford, Louth, Mayo, Meath, Monaghan, Offaly, Roscommon, Sligo, Tipperary, Waterford, Westmeath, Wexford and Wicklow — the twenty-six counties as the country listing spells them, read 2026-08-07.
A parcel may be addressed to a street address or to a post office box. The telephone number rule differs between the two, and the difference is worth respecting: a local number for the addressee should be provided for a street address and must be provided for a box. Express items carry the same instruction on their own note, along with the requirement that both the county and the city appear.