Quote Originally Posted by kdevitt View Post
The transport company my brother was in touch with said that the car will not get out of the port without the customs paperwork being all in order

Edit -
Not sure on how rigidly that could be policed (since you could drive in through NI) but seems like it should be compliant before entering Ireland

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Importing a vehicle from Great Britain (GB)
From 1 January 2021 vehicles imported from Great Britain are liable to:

customs duty, if applicable
Vehicle Registration Tax (VRT)
VAT at the current standard rate.
An electronic customs declaration will be required in advance of the vehicle arriving in the State.

Unless they inspect every UK reg car coming off the boat how would they know?