Upon pre-registration, a permanent number is assigned to the vehicle. If license plates were ordered along the pre-registration, their production takes 3 business days. After being cleared by customs, the vehicle may be moved to the inspection post that was indicated on the application for the pre-registration, where the inspection is carried out and license plates are placed on the car/vehicle. You can find more information here about the pre-registration process: https://island.is/en/pre-register-vehicles