From February 2019 there are new rules for when MOT must be carried out. Earlier, it was the last number in the license plate number which decided when the vehicle should be controlled. Now, you can choose when you want to complete the MOT, as long as the vehicle is approved within the MOT expiry date. The expiry date is final.
In practice, this means that the MOT expiry date that you already have in February rules until you have completed a new MOT. Then you get a new expiry date based on the date you do the test. The MOT intervals remain the same as today. In most cases, passenger cars have to complete the first MOT after four years and then every other year. Vehicles over 7500 kg must complete a MOT each year.
(Norwegian Public Roads Administration)