(2) Where the tax as imposed or varied by the order is modified by the Act imposing the tax, or by the resolution confirming the order, as the case may be any money which has been paid under the order, which would not have been payable under the new conditions affecting the tax, shall be repaid or made good, and any payment or deduction made under the order shall, so far as it would not have been authorised under the new conditions affecting the tax, be deemed to be an unauthorised payment or deduction.