157Effect of alteration of rates of child benefit
(1)Subsections (3) and (4) of section 155 above shall have effect where there is an increase in the rate or any of the rates of child benefit as they have effect in relation to the rate of benefit to which that section applies.
(2)Where in connection with child benefit—
(a)any question arises in respect of a period after the date fixed for the commencement of payment of child benefit at an increased rate—
(i)as to the weekly rate at which a person is contributing to the cost of providing for a child; or
(ii)as to the expenditure that a person is incurring in respect of a child; and
(b)in determining that question account falls to be taken of contributions made or expenditure incurred for a period before that date,
the contributions made or expenditure incurred before that date shall be treated as increased in proportion to the increase in the rate of benefit.