The article examines the passive voice in Slovenian with the participle -n/-t. The same participle can also express the state after a finished action and that can be problematic. Toporišič proposed the transformation rule when transforming form active to passive voice (an vice versa) should the verbal tens and aspect not be changed. With a corpus method, 300 examples from Corpus of Academic Slovenian will be examined. The analysis shows that the use of the transformation rule is not always reliable. To mark an example as passive or not, is important to recognize the messenger's intention and context of the occurrence. The other problem is also that some verbs do not have corresponding participles which means, that such an example cannot be the passive one, but that is not true.