Right thing to do, if you notice your colleague cheating your firm? I mean if you discover that there is a corruption taken place in your own firm?

if i notice that my colleague is cheating our firm? I would investigate his actions first to be sure, then i would inform the firm administration with the evidences i had, i believe that any society or party is like one body, if any part of it got ruined the whole body got sick, that's why i believe that who cheated on us is not one of us