The identical input options criterion requires that all voters have the same set of options for casting their ballot. If there exists some voter who can cast a vote that another voter cannot cast, then this criterion is not met.

More formally, a voting method $m$ passes the identical input options criterion if there exists some set of valid ballots $B$ such that a list of ballots $b_1, b_2, \dots, b_n$ is in the domain of $m$ if and only if $b_1, b_2, \dots, b_n \in B$.

The identical input options criterion is implied by the anonymity criterion and by the cancellation criterion.