Do I need to create a W2c / W3c Correction if the retirement box is not checked on original W2 / W3 which were filed in January ? (S-corp contributed to owner SEP)

Scorp contributed 25% to owners SEP but the W2 does not have box 13 checked on W2 . Does Scorp need to file a correction with the box being checked ? 

I assume there is no amount that needs to be entered on employees W2 since it is a contribution to a  SEP . 

Is there a deadline to file a W2 / W3 correction ? 

if so is there a penalty for submitting the correction with box 13 being checked .