(1) If you have any * luxury car tax adjustments that are attributable to a * tax period applying to you, alter your * net amount for the period as follows:
(a) add to that net amount for the period the sum of all the * increasing luxury car tax adjustments (if any) that are attributable to the period;
(b) subtract from that net amount the sum of all the * decreasing luxury car tax adjustments (if any) that are attributable to the period.
(2) A * luxury car tax adjustment must be made within 4 years after the supply or * importation to which the adjustment relates.