13. A local charging authority, to which a board issues a special levy under these Regulations in respect of a financial year, shall pay the amount of the special levy in that financial year–
(a)at such time and in such instalments (if any) as may be agreed between the board and the local charging authority; or
(b)in default of such agreement, by two equal instalments due on 1st May and 1st November in the financial year, or when the special levy is issued after 30th April in the financial year, due 30 days after the date of issue of the special levy and on 1st November or 60 days after the said date of issue (whichever is later).