Spoilt vote

Spoilt ballot paper from the 2016 Kazakh legislative election reading "Бойкот Выборам" which means Boycott the elections.
Spoilt ballot paper from the 2021 UK Police and Crime Commissioner Elections

In voting, a ballot is not included in the vote count if a law declares or an election authority determines that it is spoilt (chiefly British), spoiled (chiefly American), void, null, informal, invalid, rejected or stray. This may occur accidentally or deliberately.

The total number of spoilt votes in a United States election has been called the residual vote.

In some jurisdictions, spoilt votes are counted and reported.