A person normally resident in the UK may drive a UK registered car for up to 12 months in Ireland.I wonder when the government (Revenue) will properly go after UK/Northern Ireland registered vehicles being used as daily drivers over here. I see the same cars and vans daily, some of them for years.
They can have it extended by applying to revenue.
https://www.gov.ie/en/service/716b1-what-to-do-if-you-are-taking-a-vehicle-into-ireland-temporarily/
I'm sure some flout the rules but are able to have enough paperwork to squeeze by