Section 28 in Presidential And Vice-Presidential Elections Rules, 1952
28. Ballot papers when invalid.-
(1)A ballot paper shall be invalid on which-(a)the figure 1 is not marked; or(b)the figure 1 is marked opposite the name of more than one candidate or is so marked as to render it doubtful to which candidate it is intended to apply; or(c)the figure 1 and some other figure are marked opposite the name of the same candidate ; or(d)any mark is made by which the elector may afterwards be identified.(2)A ballot paper shall also be invalid if, being a postal ballot paper, the signature of the elector is not duly attested.
