noun
invalid vote; spoiled ballot
Refers to a vote that is not counted because it does not meet the rules, such as writing outside the designated space or marking multiple candidates.
選挙で無効投票が増えると、民意が正確に反映されない。
When invalid votes increase in an election, the public will is not accurately reflected.
白票 is a blank ballot, which is one type of invalid vote, while 無効投票 covers any invalid ballot including those with unclear markings.
Compound of 無効 (invalid) and 投票 (vote).