5. For regulation 23(5)(c) substitute—
“(c)for any subsequent quarterly period that includes 1st April of any year, the value of A in the previous quarterly period adjusted by the percentage increase or decrease in—
(i)the retail prices index for the previous calendar year, if the tariff start date is earlier than 1st April 2016; or
(ii)the consumer prices index for the previous calendar year, if the tariff start date is on or after 1st April 2016,
the resulting figure being stated to two decimal places and rounded.”.