The present invention provides a clip nut which prevents the installation when the clip nut is used and the license plate is installed to a back bumper through a clip bolt and the clip bolt is longerthan a preset dimension so as to prevent the damage to the vehicle body, etc. through the clip bolt. A clip body (30) is integrally provided with a protecting sheet (40) which is opposite to the frontend of a clip bolt (CB). When the length of the clip bolt (CB) exceeds a preset value, the front end of the clip bolt (CB) pushes the protecting sheet (40) thereby preventing the fastening between arear bumper (RB) and the license plate (LP).