Paragraph 17 Receipt of covering envelope
(1)
The constituency returning officer shall, immediately on receipt (whether by hand or by post) of a covering envelope (or an envelope which is stated to include a postal vote) before the close of the poll, place it unopened in a postal voters' ballot box.
(2)
Where an envelope, other than a covering envelope issued by the constituency returning officer–
(a)
has been opened; and
(b)
contains a ballot paper envelope, declaration of identity or ballot papers,
the first–mentioned envelope, together with its contents, shall be placed in a postal voters' ballot box.