I am a lawful permanent resident of the U.S., can I leave the U.S. multiple times and return?
If you are a lawful permanent resident (green card holder), you may leave the U.S. multiple times and reenter, as long as you do not intend to stay outside the U.S. for 1 year or more.
If you intend to stay outside the U.S. for 1 year or more, you must apply for a re-entry permit with the U.S. Customs and Immigration Service (USCIS) prior to leaving the U.S. Re-entry permits are generally valid for 2 years from the date of issuance. Therefore, if you are outside of the U.S. longer than the date the permit was issued, you may be denied entry into the U.S.
To apply for a re-entry permit, you must file an Application for a Travel Document (I-131) with the USCIS. If you applied for permanent resident status, but are not yet officially a lawful permanent resident "green card holder" and you need to leave the U.S. on emergency, you must apply for and receive advance parole to leave the U.S. by filing a I-131 with USCIS. Information on how to file the I-131 is available here.
If you are required to file documents prior to leaving the U.S., it is imperative that you do so, otherwise, you may be found inadmissible and denied reentry into the U.S.
If you are a green card holder and you do not stay outside the U.S. for 1 year or more, you should have either your green card (INS Form I-551, or your returning resident visa to re-enter the United States. You are not required to present your unexpired passport, however it is not a bad idea to carry it with you.
What documents, identification, and paperwork does a legal permanent resident (LPR) or Green Card holder need to travel internationally?
Lawful Permanent Residents (Green Card holders) do not need a passport to enter the United States, however, they may need a passport to enter another country. Please contact the embassy of the foreign country you will be traveling to for their requirements. Note: Canada does not require a passport from U.S. LPR's.
Lawful Permanent Residents of the U.S. must present a Permanent Resident Card ("Green Card", INS Form I-551), a Reentry Permit (if gone for more than 1 year), or a Returning Resident Visa (if gone for 2 years or more) to reenter the United States. U.S. LPRs are not required by the U.S. to have a passport for travel within the Western Hemisphere, although most foreign destinations will require you to have one to enter their country (LPRs that are out of the U.S. for more than 180 days are subject to new immigrant inspection procedures as per 8 USC 1101).
Foreign nationals that have applied for permanent residency may need to be approved for advance parole (prior to traveling out of the U.S.) in order to be readmitted when traveling back to the U.S. (H1, H4, L1, L2, K3, K4 or V2, V3 holders do not require advance parole to travel abroad after applying to adjust status