Before coming to the United States, you were issued a passport by your government allowing you to leave and re-enter your own country. Your passport must always be valid for a period of six months longer than you expect to stay in the United States. If necessary, your own consulate or embassy in the U.S. will extend your passport. Consult with them to learn what forms and fees are required. If you have a valid U.S. visa in an expired passport you can still use the visa as long as it is presented at the port of entry together with a new and valid passport.
The U.S. visa is the label placed by a U.S. consular office on a page of your passport. It indicates that the consular office has determined that you are qualified to apply for admission to the U.S. in a particular immigration classification. A valid visa does not ensure an alien's entry into the U.S.; an immigration officer at the port of entry makes this decision.
The expiration date on the visa does not have any relationship to the length of time you can stay in the U.S., only to the length of time it is valid to present to immigration when applying for entry to the U.S. The duration of your legal stay in the U.S. will be noted on your Departure Record, also known as Form I-94.
Form I-94 records your arrival date in the U.S., the type of visa you hold, and your expected date of departure from the U.S., and should remain in your passport until you depart the U.S. F-1 and J-1 visa holders will get a notation, D/S, meaning duration of status.
When you completed the I-94 upon arrival in the U.S., you also gave your initial address in the U.S. If you are subject to Special Registration, you must remember to complete form AR-11 SR every time you change your address after your initial entry to the U.S. For all other F-1 and J-1 students, you must inform the International House of any address change in order for us to update your SEVIS record.
H and O visa holders must complete form AR-11. With the latest changes in immigration regulations, it has become very important that you maintain your status; failing to do so can have serious consequences, including being denied entry to the U.S.