Where an authority sets any amount in substitution under section 34 or 35 above (a new amount) anything paid to it by reference to the old amount shall be treated as paid by reference to the new amount.
But if the old amount exceeds the new amount, the following shall apply as regards anything paid if it would not have been paid had the old amount been the same as the new amount—
it shall be repaid if the person by whom it was paid so requires;
in any other case it shall (as the charging authority determines) either be repaid or be credited against any subsequent liability of the person to pay in respect of any community charge of the authority.
Where an authority sets an amount or amounts in substitution under section 35(1) above it may recover from the precepting authority administrative expenses incurred by it in, or in consequence of, so doing.
For the purposes of this section the old amount is the amount found by—
taking the amount, or each of the amounts, for which the new amount is substituted (whether directly, or indirectly because of one or more intermediate substitutions),
leaving out of account any amount to which section 35C(4) above applies, and
taking the amount remaining or (if more than one remains) the last to be set.