As a green card holder you can travel outside the U.S., but if you intend to stay outside the U.S. for over a year you will need a re-entry permit, former I-131. If you don’t your green card may be considered abandoned.A reentry permit establishes that you did not intend to abandon your status; it allows you to apply for admission to the U.S. after traveling abroad for up to two years without having to obtain a returning resident visa.You should file form I-131, application for a travel document, at least 60 days before you intend to leave the U.S.