Reentry Permit Application
Are you a green card holder who is planning to travel out of the United States for over a year but less than two years? If yes, you will need to file reentry permit application with the USCIS and get reentry permit before leaving else you will lose your permanent residency. A border and customs officer will then deny you entry into the United States. You will have to go back and apply for an entry visa from a US consulate.

A reentry permit is a travel authorization document given to a green card holder who is leaving the country for over a year. A green card holder is required to maintain a continuous residence in the United States. They cannot be gone for a period of over 1 year else they abandon their residency. However, if you have specific circumstances that require you to travel then you have to tell the USICS why you need to travel and get a reentry permit. This way the US customs and border officer will not consider your time out of the country as absent from the country because of your permit.
To apply for a reentry permit, you file the Form I-131, also called the application for a travel document. You submit the form within the United States at least 60 days before your travel along with supporting documents and filing fees. You do not have to stay in the country for the reentry permit to be approved but you have to be here when you file it because they send you for biometrics.
A reentry permit is issued for 2 years. You cannot extend the permit. You need to return to the United States but you can then file for a new reentry permit. Be sure to return before the two years end or once again you could lose your residency.