I can understand that if the car is being imported commercially and back until 1993 when the single market came in to effect and VRT was introduced the car had to be declared at the port of arrival and couldn't be removed until all duty, VAT, etc. was settled and the paperwork stamped.
Here - https://www.revenue.ie/en/importing-...e-from-gb.aspx there's a comment:
"Where a customs declaration is required in respect of a vehicle brought into the State, the vehicle will be liable to seizure if the customs declaration is not completed and, or the vehicle is not registered within 30 days of its arrival in the State."