The Irish Standard for Hygiene in the Catering Sector, which serves as the guide for compliance with EU Regulation 852/2004.
This is the main standard for Irish food businesses. Your HACCP plan must be based on this standard. If you buy a generic HACCP folder from the UK or US, it will likely reference different standards and will not pass an Irish EHO inspection.
You can get the standard from the NSAI (National Standards Authority of Ireland). However, the FSAI provides comprehensive "Safe Catering" packs which are based entirely on I.S. 340:2007. For most hospitality operators, following the FSAI Safe Catering pack is the most practical way to implement the standard without needing to memorise the raw text of the document.
It is the National Standard for Hygiene in the Catering Sector. While it is a "standard," compliance with it is the primary way businesses demonstrate they are meeting the legal requirements of Regulation (EC) No 852/2004. If you are following I.S. 340:2007, you are deemed compliant. If you choose not to follow it, you must prove your alternative method is equally safe, which is difficult and expensive for most SMEs.