Spoilt vote

A ballot may be spoilt in a number of ways, including: As an example, UK law specifically precludes ballots "on which votes are given for more candidates than the voter is entitled to vote for", "on which anything is written or marked by which the voter can be identified" or "which [are] unmarked or void for uncertainty".

In Canada, a spoiled ballot is one that has been handled by an elector in such a manner that it is ruined beyond use, or that the deputy returning officer finds soiled or improperly printed.

When the election jurisdiction does not report voter turnout, roll-off can be used as a proxy for residual votes.

Some voters may only be interested in voting for the major offices, and not bother filling in the lower positions, resulting in a partially valid ballot.

[6] Albert Langer was jailed for violating an injunction not to advocate incomplete preference voting for the 1996 Australian federal election.

Some election officials have discretion to allow ballots where the criteria for acceptability are not strictly met but the voter's intention is clear.

When multiple Irish STV elections are simultaneous (as for local and European elections) some voters have marked, say, 1-2-3 on one ballot paper and 4-5-6 on the other; some returning officers consequently allowed 4-5-6 ballots to be counted, until a Supreme Court case in 2015 ruled they were invalid.