An Alien Registration Card, commonly known as a green card, is evidence of your status as a Lawful Permanent Resident with the right to live and work permanently in the United States. The Permanent Resident Card is also called Form I-551. If you were issued a green card with a validity period of 10 years, and is about to expire, then you have to renew it. For renewal of an expired green card you need to use Form I-90,Application to Replace Permanent Resident Card. If you are a Permanent Resident and you were issued a "Green Card" valid for ten years, and that the card is either expired or will expire within the next six months then you must renew your Permanent Resident Card. Even if you do not renew your green card, you will not lose your permanent resident status - your permanent resident status will not expire or change. However, you are required by law to carry evidence of your status/registration like a valid, unexpired green card or the temporary proof of status you receive at the time of renewal of an expired green card application was filed. If you fail to renew your Green card, you may experience difficulties in obtaining employment, benefits and re-entry into the United States from abroad. If you are a Conditional Permanent Resident and you obtained your Conditional Permanent Residency through marriage to a US citizen, you will need to submit a Petition to Remove Conditions on Residence (Form I-751) within 90 days before your conditional permanent residency expires. If you are not certain of the type of Permanent Resident you are, check your green card and see if it has a two year expiration date (Conditional Permanent Resident) or a ten year expiration date (Permanent Resident). If you are a Conditional Permanent Resident then you need to apply for Form I-751 to remove the conditions on your Conditional Permanent Resident card. If your green card has a 10 year expiration and it is going to expire within the next six months then you need to file Form I-90 for renewal of an expired green card. You need to apply for Form I-90 to replace your green card before you can travel. Once you have filed for Form I-90 you can get your passport stamped with I-551 at the local USCIS office to indicate that you have filed for a new card. The I-551 stamp in the passport is the proof of Lawful Permanent Resident status of the passport bearer. It will enable a person to travel out of the US and re-enter as the stamped passport indicates, the person has filed for green card replacement as required by law. If your permanent resident card will expire within six months and that you are outside the United States, (but you will return within one year of your departure from the United States and before the card expires), you should file for renewal of an expired green card. as soon as you return to the United States. If you are outside of the United States at the time of the cards expiration, and you have not applied for the renewal of an expired green card prior to your departure, you should contact the nearest American Consulate, USCIS office, or Port of Entry, before attempting to file Form I-90 for renewal of an expired green card.