The Communications Minister says 'we can't expect' to have the new postcode service 'finalised' on its first day.
Alex White was responding to criticisms of the new Eircode system which he launched earlier.
2.2 million homes and businesses across the country will be assigned an individual 7 digit 'Eircode' - which they will receive in the post in the coming weeks.
Dublin's codes will start with the letter D - with current postcodes like Dublin 1 becoming D01.
Cork City is expected to get the letter T - while Galway to get H.
Freight companies including FedEx and DHL say they won't use the service because it's 'outdated' - and the unique 7 digit codes are not searchable on Sat Navs or Google Maps.
Meanwhile, people have been using social media to complain about their homes being marked in the wrong towns, counties or provinces.
But Minister Alex White says Eircode is 'more than worth' the 27 million euro outlay.
