Blacknight - An Post is not the authority for recognising Post Codes in Ireland. A National Post Code system was supposed to be introduced by Jan this year but it appears now that it is on the long finger due to opposition by the semi state commercial body that is An Post and because of economic issues. In the meantime all the usual well documented difficulties related to not having a Post Code system remain. Interestingly, the biggest demand for Post Codes is not from those sending mail but rather those operating on the web or delivering services via vehicles on our roads (Including Courier Services and Fire and Emergency Services). PON Codes are Lat/long or grid references in a different format - many have tried using Lat/long as an alternative to Post Codes in Ireland to resolve problems but they are too difficult to use/remember/communicate for those who have no knowledge and come in too many formats. PON Codes solve these problems and in the absence of nothing else there is is nothing to stop anyone using them on the web or on satnav's...... they are precise and they work and, indeed, they may well become the National System if and when that is implemented!!!!

All expalined here: PONC Find Out More

and here:
GPS Ireland Ltd - Nationwide GPS & SatNav Services - Location (Post) Codes For Ireland