Advance Parole is a document for certain aliens, whose I-485 application for adjustment of status is pending, to re-enter the United States after traveling abroad. There are two purposes for advance parole. First, it preserves the alien's I-485 pending status at the USCIS. Second, it enables the alien come back to the U.S. after traveling abroad without the necessity of obtaining a visa to the U.S. Such aliens must be approved for Advance Parole before leaving the United States. If they have not obtained Advance Parole prior to traveling abroad, they will not be permitted to re-enter the United States upon their return.
An Re-Entry Permit is issued by permanent residents or conditional permanent residents who wish to remain outside the U. S. for a prolonged period of time, but less than two years. A re-entry permit usually enables a permanent resident, who traveled abroad for a period of time of more than one year but less than two years, to avoid the risk of not being allowed to come back the U.S. on the ground that the alien abandoned his permanent residence status. A re-entry permit can also serves as a passport for a permanent resident who wants to travel outside the U. S., but cannot get a national passport from his country of nationality.