79.—(1) Where a person has been paid a sum of housing benefit under a decision which is subsequently revised or further revised, any sum paid in respect of a period covered by a subsequent decision shall be offset against arrears of entitlement under the subsequent decision except to the extent that the sum exceeds the arrears and shall be treated as properly paid on account of them.
(2) Where an amount has been deducted under regulation 85(1) (sums to be deducted in calculating recoverable overpayments) an equivalent sum shall be offset against any arrears of entitlement under the subsequent decision except to the extent that the sum exceeds the arrears and shall be treated as properly paid on account of them.
(3) No amount may be offset under paragraph (1) which has been determined to be an overpayment within the meaning of regulation 80 (meaning of overpayment).