Ireland does not have general retrospective planning permission, but it does have a similar mechanism called retention permission, which allows a local authority to assess and, if appropriate, permit works that have already been carried out. Retention is assessed against the same planning criteria as a normal application and is not guaranteed to be granted.
The term 'retrospective planning permission' is often used loosely, but the correct Irish mechanism is retention permission under the Planning and Development Act 2000, which allows an application to be made for works that have already been constructed or a use that has already commenced without the necessary permission. A grant of retention permission has broadly the same legal effect as an ordinary permission, formally authorising the development from that point, though it does not retrospectively excuse any enforcement action that may have already occurred.
Retention applications go through the same public notification, statutory consultation, and assessment process as a standard planning application, and are judged against the local authority's development plan, ministerial guidelines, and normal planning considerations such as impact on neighbours, character of the area, and road safety. The fact that the works already exist does not guarantee approval; a planning authority can and does refuse retention where the development is considered unacceptable, and refusal can trigger enforcement requiring removal.
Retention permission is commonly sought where unauthorised works are otherwise reasonable in planning terms, such as a slightly oversized extension, or where an error was made in relation to exempted development limits, siting, or building lines. It is generally not available, or unlikely to succeed, where works were built in defiance of an earlier refusal for similar development, or where they cause serious planning harm.