Your Permanent Resident Card shows that you are allowed to live and work in the United States. You can also use it to re-enter the United States after traveling abroad. If you are outside of the United States for more than 12 months, then you will need to show additional documentation to re-enter the country as a permanent resident.
Maintaining Your Permanent Resident Status
Once you have obtained permanent resident status, you will continue to be a permanent resident unless your status changes as provided under U.S. immigration law. One way you can lose permanent resident status is by abandoning it. You abandon your permanent resident status by leaving the United States to live abroad permanently with the intent of giving up your permanent resident status. Your conduct will demonstrate your actual intent. There are some things you can do to decrease the possibility that the U.S. government will find that you have abandoned your status:
1. Do not leave the United States for an extended period of time unless the circumstances show that your trip is for a temporary purpose (for example, to attend school, take a temporary job, or care for a family member). If you are absent for a year or longer, you cannot use your Permanent Resident Card to enter the United States.
2. If something happens that delays your return, be prepared to explain the reason(s) for the delay.
3. File federal and, if applicable, state, and local income tax returns.
4. Register with the Selective Service if you are a male between the ages of 18
5. Give your new address to USCIS within 10 days of each time you move.