Motorists are being urged to tax vehicles which they have brought over from the UK.
The Roads Policing Unit says it will be "pro-actively" checking UK registered vehicles and will prosecute.
UK vehicles which are over three years old also have to be booked into the Test Centre – paperwork must be completed for vehicles which are less than three years old.
Officers say this must be done as soon as possible saying using a UK registered vehicle for months without registering it is "unacceptable" and you may be prosecuted.
