The postal district appears with one or two digits (or in the case of one district, a digit and a letter) appearing at the end of addresses, e.g.:
Primarily, odd numbers are used for addresses on the Northside of the River Liffey, while even numbers are on addresses on the Southside. Exceptions to this are the Phoenix Park (along with a small area between the Park and the River Liffey), and Chapelizod Village which, whilst being on the Northside of Dublin, are parts of the Dublin 8 and Dublin 20 postal districts respectively.
The districts have been added to as the city grew, and large districts have been subdivided, as when Dublin 5 was split, with the coastal part retaining the "5" and the inland part becoming Dublin 17.
In 1985, Dublin 6 was divided, with some areas, such as Templeogue, Kimmage and Terenure becoming part of a new district in order to facilitate processing of mail by a new sorting office for those areas. Residents of some areas objected to the assignation of the next available number, "Dublin 26," for the new postal district, citing property devaluation (the higher numbered districts typically representing less affluent, and typically less central regions). An Post ultimately relented, and the district became known as Dublin 6W (Confusingly the Eastern half of the old D6 postcode area remained "Dublin 6" rather than "Dublin 6E").
Proposals to extend the system to Blackrock (a wide area of southern suburbia has the postal designation "Blackrock," far beyond the actual district of that name) and Dún Laoghaire met with similar objections to those which arose with Dublin 6, so the numbering system is not used for surrounding areas in County Dublin, such as Dún Laoghaire, Blackrock, Lucan or Swords.
In Cork, there are also numbered districts, eg: the 'PATRICK STREET' (Sráid Phádraig) sign will display the digit '1', but these are not encountered in postal addresses. Cork has four postal districts. District 1 covers the city centre and large parts of the surrounding city. District 2, administered from the Ballinlough sorting office covers the south-east, District 3 (from Gurranabraher) covers the north-west while District 4 (from Togher sorting office) covers the south-west. In practice these numbers are only used internally by An Post and rarely used on mail.
Ireland's Minister for Communications, Marine and Natural Resources, Noel Dempsey, announced that postcodes would be introduced in Ireland by 1 January 2008. It was reported that the postcodes would include the one- and two-character county codes currently used in vehicle registration plates, and that each address would have a unique postcode. (With the existing Dublin system retained.) However, in August 2007, the new Minister reportedly postponed the implementation of the system "indefinitely", pending additional public consultation.
In a speech at a Comreg conference on Postal services on October 18th 2007 the Minister committed himself to the introduction of a post code system as soon as possible.Industry sources say it will be at least 2009 though before they could be introduced