(iii) the duty paid on the goods concerned shall be deemed to have been paid on the date on which the permit referred to in paragraph (a) was issued. (Added A/11/1988; amended A.5/1991.) (16ter) (a) Subject to the provisions of subsection (16bis), any authorised official, or the Commissioner, may in respect of goods which may, in terms of any item of Schedule No. 3, 4, 5 or 6, be entered under rebate of duty or be subject to a drawback or a refund of duty, issue, subject to such conditions as such authorised official or the Commissioner may specify, with or without retrospective effect, a permit or certificate authorising entry of those goods under rebate of duty, or authorising a drawback or a refund of duty in accordance with the provisions of the item concerned: Provided the Commissioner is satisfied in respect of the goods concerned, where the permit or certificate concerned is issued with retrospective effect, that the provisions of such item and such conditions have been complied with. (b) Subsection (16bis)(b) shall apply mutatis mutandis in respect of any permit or certificate referred to in paragraph (a). Application for such permit or certificate shall be made to the authorised offi(c) cial referred to in paragraph (a) or the Commissioner within six months from any date specified in section 39(5)(a), (b) or (c), as the circumstances may require. (Added A.5/1991.) (17)(a) The Minister may from time to time by notice in the Gazette amend Schedule No. 3, 4, 5, 6 or 7 and any such amendment may be or retrospective effect from such date as may be specified in such notice. (b) An amendment made under paragraph (a) which — (i) repeals any existing provision in Schedule No. 5 or which excludes any goods from any existing provision of that Schedule, shall not apply in respect of goods, excluding distillate fuels referred to in item 533.01 of Schedule No. 5 which were imported prior to the date of the relevant notice in the Gazette; and (ii) embodies any additional provision in that Schedule applies any existing provision of that Schedule in respect of additional goods, shall not except in so far as the Commissioner so directs and subject to such conditions as he may determine, apply in respect of goods which were imported prior to the date of the relevant notice in the Gazette. (Amended A.7/1981; A.5/1991.) (18)The Commissioner may refuse to accept an entry under rebate or any application for drawback or refund under any item of Schedule No. 3, 4, 5, 6 or 7 from any person who has persistently contravened or failed to comply with this Act or has committed an offence