4.—(1) Subject to the provisions of this Article and of Articles 5 and 6 the amount of each assessment appearing in an assessment notice served by the Board shall be due and payable to the Board in two instalments and the said instalments shall be due respectively on 1st October 2002 and 1st February 2003.
(2) Where an election has been made the amount of the assessment appearing in each assessment notice shall be payable to the Board in one instalment due one month after the date of the notice.
(3) An instalment of an assessment shall not be recoverable by the Board until there has expired the time allowed for appealing against the assessment by Article 6(1) and any further period of time that the Board or an industrial tribunal may have allowed for appealing under Article 6(2) or (3) or, where an appeal is brought, until the appeal is decided or withdrawn.