6(1)Every ballot paper must bear or contain—S
(a)an official mark on the front of the ballot paper, and
(b)a unique identifying number on the back of the ballot paper.
(2)The counting officer may use a different official mark for ballot papers issued for the purpose of voting by post from the official mark used for ballot papers issued for the purpose of voting in person.
(3)The counting officer may use a different official mark for different purposes.
(4)The official mark must be kept secret.