A U.S. permanent resident has the right to travel freely in an out of the country. This is one the benefits of having a green card. You do not have to apply for any visa or any other authorization to be able to return to the U.S. When you arrive, you simply show the U.S. Customs and Border Protection, CBP, officer your green card along with your other travel document (in most cases, a passport).
However, if you’ve lost your green card before your trip (you are still in the U.S.) or after your trip (you are abroad) you will need to apply for permission be able to reenter the U.S.
Lost green card before trip
If you’ve lost your green card before your trip, it’s best to file Form I-90, Application to Replace Permanent Resident Card while you’re still in the states. Getting a replacement green card before you leave can help you avoid complications.
It’s important to know that the process of replacing a lost green card generally takes six months. Though you may request to expedite your application, expedite requests are only granted on a case-by-case basis in special circumstances.
If you can’t wait to get your replacement green card, you may need to file a Form I-131A, Application for Travel Document (Carrier Documentation). The form, once approved, allows you to board the plane or other transportation when you are heading back to the U.S. In most cases, a transportation carrier taking passengers to the U.S. will not allow you to board unless you have an authorization because they can be penalized by law.
Once you arrive at the port of entry in the U.S., you will show your travel document obtained through Form I-131A and explain your situation to the CBP officer. There, you may be asked to file (and pay the fees for) Form I-90 to replace your green card. You will need to plan for those fees and for the extra time you will have to spend with CBP trying to gain entry back into the states.
Lost green card during trip
If you lost your green card during your trip, you should contact the U.S. consulate in the country where you are staying. The consulate may have its own guidelines for such situations. They may be able to even grant you a special boarding foil (also known as a transportation letter), for example.
It is also possible that they will tell you-you’ll need to file a Form I-131A, Application for Travel Document (Carrier Documentation) as well. As mentioned above, this form, once approved, can let you board the plane or other transportation to get back to the U.S. The form is necessary because a transportation carrier taking passengers to the U.S. can’t allow you to board unless you have an authorization. If they don’t check that you have authorization and let you arrive in the U.S. without one, they can be penalized by law.
The U.S. consulate may also recommend that you file a police report abroad if you think your card was stolen and take it with you when you return to the states.
Once you arrive in the U.S, you can show your travel document obtained through Form I-131A and any police reports from the country you visited stating your green card was stolen. When you explain the situation to the CBP officer, you may be asked to file (and pay the fees for) Form I-90 to replace your green card. All of this might take a long time, so be sure to be prepared for that.