PART 8Payments to discharge the renewables obligation, dealing with the buy-out and late payment funds, and mutualisation
Calculating the total mutualisation sum in the case of a relevant shortfall
73.—(1) Subject to paragraphs (2) to (4), where a relevant shortfall has occurred in relation to the relevant period, the total mutualisation sum for that period is the amount of that shortfall.
(2) Where any non-compliant UK supplier has produced UK ROCs to the Authority or the Northern Ireland authority in order to discharge, in part, any UK renewables obligation to which it was subject in the relevant period, the total mutualisation sum for that period is equal to 
(a)S, subject to paragraphs (3) and (4), is the amount of the shortfall;
(b)C is the number of UK ROCs produced by non-compliant UK suppliers to the Authority or the Northern Ireland authority in order to discharge, in part, any UK renewables obligation to which they were subject in the relevant period; and
(c)D is the total number of UK ROCs produced by UK suppliers to the Authority or to the Northern Ireland authority in order to discharge, in whole or in part, any UK renewables obligation to which they were subject in the relevant period.
(3) If the total mutualisation sum for the relevant period has to be recalculated by virtue of article 75(5), for the purposes of that recalculation (whether under paragraph (1) or (2)) the amount of the shortfall is to be reduced by the sum of all payments mentioned in article 75(1)(b) received by UK suppliers.
(4) For the purposes of calculating or recalculating the total mutualisation sum for the relevant period, the amount (if any) by which the shortfall in relation to that period exceeds the mutualisation cap for that period is to be disregarded.
(5) The mutualisation cap for the relevant period depends on which obligation period constitutes the relevant period and is—
(a)for the relevant period commencing with 1st April 2016, the 2015/16 mutualisation cap increased or, as the case may be, decreased by the percentage increase or decrease in the retail prices index over the 12 month period ending on 31st December 2015 (the resulting figure being rounded to the nearest penny, with any half of a penny being rounded upwards); and
(b)for each obligation period thereafter, the mutualisation cap for the previous obligation period increased or, as the case may be, decreased by the percentage increase or decrease in the retail prices index over the 12 month period ending with the 31st December in the previous obligation period (the resulting figure being rounded to the nearest penny, with any half of a penny being rounded upwards).
(6) In paragraph (5), the “2015/16 mutualisation cap” is £267,035,558.91.