4(1)The rate of the person’s state pension under section 13 is to be increased under this paragraph if, when added to the total amount of any state pension that has priority, it is equal to or less than the full rate of the state pension.
(2)If at any time the full rate is increased, the rate of the person’s state pension under section 13 is increased (at that time) by the same percentage as the increase in the full rate.