(iii) any such distillate fuel purchased shall be deemed to have been used in the order of the dates of such purchases; (iv) the extent of the refund referred to in subparagraph (i) shall be the rate of such refund specified in such item of Schedule No. 5 or 6 in operation on the date of issue of the invoice concerned, referred to in subsection (4bis)(b)(ii); (i) if the extent of such refund is amended and for any reason any liability to repay any refund of duty in respect of any quantity of fuel which the user may incur cannot be assessed or the amount of duty refundable to such user in terms of any item of Schedule No. 5 or 6 cannot be calculated on any quantity of such fuel purchased by such user before such amendment, the quantity of such fuel in respect of any refund which the user is liable to repay, or the quantity used in accordance with any such item for the calculation of the amount refundable to such user, shall be determined by the Commissioner according to the information at his disposal; (Amended A.5/1991.) (g) any refund referred to in subparagraph (f)(i) may be granted and paid to any person entitled to that refund in terms of this Act, by any official of any administration to which the moneys concerned have been rendered available by the Commissioner. (Added A.5/1991.) (1bis) (a) Notwithstanding anything to the contrary in this Act, the Commissioner may subject to such conditions as he may impose, allow in respect of any refund referred to in subsection (1)(f)(i) any person to grant a provisional refund of duty to any registered user of distillate fuel who purchases such fuel from that person. (b) Any provisional refund shall be granted in accordance with an estimate of intended use furnished by such user to the person concerned. The Commissioner may pay to such person or allow him to set off in terms of (c) section 77 against duty for which he is liable, any amount which he granted to such registered user at such times and on furnishing of such particulars as the Commissioner may specify. (d) Any amount paid in error by the Commissioner to such person shall be recoverable from such person as provided in section 76bis. (e) The Commissioner may cancel the said registration of such person if such person claims or receives any amount or payment to which he is not entitled. (f) Any provisional refund granted by such person to such user shall, subject to paragraphs (g), (h) and (i), he deemed to be a refund paid by the Commissioner in terms of subsection (1)(f)(i).