One of the advantages of having a green card and therefore permanent residency is that you can travel and re-enter the US far more easily than a visa holder. If you have traveled outside the US for less than one year, you can re-enter the US simply by showing your passport from your home country as well as your US green card.
If you have traveled outside for less than two years but for more than one year, you will need a re-entry permit as well as your home country passport and your green card to re-enter the US. You may also need a reentry permit if you cannot secure a passport from your home country for some reason.
If you will be traveling outside the US without your home country’s passport or will be traveling for an extended period of time, it is essential to secure your reentry permit before you travel. If you do not secure your re-entry permit, you may be denied entry into the US. Worse, the USCIS may interpret your travel as a abandonment of your US resident status, which could mean that you lose your conditional green card or permanent green card.
You will need to go through the entire green card application process again. For this reason, you may want to secure a reentry permit if you plan to travel outside of the US for more than five months. If you are delayed outside the country, you still have the documents to re-enter.
If you plan on traveling outside of the US for more than five months and have not yet applied for a green card, you may want to apply for a visitor visa before applying for your green card, and only apply for the green card after your prolonged trip. This will ensure you are not at risk of losing your permanent resident status due to the extended trip. Once your trip is complete, you can then apply for permanent residency.
If you have a re-entry permit, you will not need to get a returning resident visa. However, it is important to keep in mind that simply have a reentry permit does not guarantee permission of entry into the US. Border authorities as well as other authorities may still legitimately bar you from entry. You must have your re-entry permit, your supporting documentation, and you must meet all eligibility criteria for re-entering the US before you are allowed re-entry.