101.—(1) Subject to paragraph (2), in calculating the amount of a recoverable overpayment, the relevant authority shall deduct any amount of housing benefit which should have been determined to be payable in respect of the whole or part of the overpayment period—
(a)on the basis of the claim as presented to the authority;
(b)on the basis of the claim as it would have appeared had any misrepresentation or non-disclosure been remedied before the decision; or
(c)on the basis of the claim as it would have appeared if any change of circumstances, except a change of the dwelling which the claimant occupies as his home, had been notified at the time that change occurred.
(2) In the case of rent or rate rebate only, in calculating the amount of a recoverable overpayment the relevant authority may deduct so much of any payment by way of rent or rates in respect of the overpayment period which exceeds the amount, if any, which the claimant was liable to pay for that period under the original erroneous decision.