USCIS has a K Unit that tracks down multiple filers. If you have had an I-129F Petition approved recently meaning the petition got the “Go Ahead” but your alien fiancee and you had a change of heart, or you brought over your alien fiancee and things did not work out? Or you married but then divorced after a short time? You must wait for a period of two (2) years before you can file again. Or if you have good supporting evidence and documentation that supports a legitimate reason you could not marry or bring the alien fiancee over, then you can file a waiver without waiting for the two (2) years waiting time.