The K1 fiance visa is a single entry visa which means that it can only be used once to enter the United States. Thus, if the K1 visa holder is to return to the U.S. he or she will need some other sort of document or visa to return to the U.S. If the K1 visa holder leaves the U.S. without an Advanced Parole document or green card, he or she will not be able to return without obtaining a visa.

This is why it is critical that K1 visa holders do not depart the U.S. without either a travel document or green card in hand.