81.—(1) An administering authority may require an authority from which payment of any amount due under regulation 78, 79, 80, 90, 126 or 127 is overdue by more than one month to pay interest on that amount.
(2) Interest under paragraph (1) or under regulation 93(1) must be calculated at one per cent. above the base rate on a day to day basis from the due date to the date of payment and compounded with three-monthly rests.
(3) Interest under regulation 86(1) or 88(5) must be calculated at nine per cent. per annum compounded with yearly rests on 31st March.