# The Greater London Authority Elections Rules 2007, Paragraph 19: The official mark


(1) Every ballot paper must contain an appropriate security marking (the official mark).
(2) The official mark must be kept secret, and an interval of not less than five years must intervene between the use of the same official mark at any Authority election.
(3) The GLRO may use a different official mark for different purposes at the same election.

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Source: https://www.legislation.gov.uk/uksi/2007/3541/schedule/3/paragraph/19 (the official version)
Page: https://openlegislation.uk/greater-london-authority-elections-rules-2007/schedule-3/paragraph-19
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.