In negated contexts, tense and mood contrasts are not explicitly marked on the lexical
verb. It is possible to use a predicate adjective (with lexical infinitive) in order to circumvent this constraint, and there is a negative future marker (tuma) that is frequently used with (negative) habitual interpretation in present tense (but never past tense) contexts. If the lexical verb is marked as negative though, this prevents the appearance of tense markers or mood markers in the same position.
Examples:
ta-kelaatan 'did not see'
su-kelaatan 'see'
bole-kelaatan 'can/could see'