Your passport is a document issued by your government and permits you to travel abroad. You are required to keep your passport valid for at least six months into the future throughout your stay in the U.S. Please review the expiratoin date of your passport, and contact your country's embassy or consulate to renew it at least several months before it expires.
The F-1 visa is issued by a U.S. consulate overseas (ordinarily in your country of citizenship or permanent residence), and is presented upon arrival at a U.S. border or port of entry to U.S. to pursue full-time study. Students from all countries except Canada and Bermuda are required to have valid F-1 entry visas in order to request admission as F-1 students.
The expiration date of your visa is not the same thing as the expiration date of your permission to stay in the U.S. You must have a valid F-1 visa to enter the United States as an F-1 student, but you may remain in the U.S. even if the visa expires. The expiration date of your permission to stay is indicated on the Form I-94 (Arrival/Departure Record) and your Form I-20.
Before leaving on a trip outside the U.S., check the expiration date of your visa and the number of entries you are allowed. You may need to renew your visa while you are traveling abroad (see "Visa Renewals," below). Short trips (30 days or less) to Canada, Mexico, and the Caribbean do not require an unexpired visa for reentry into the U.S. However, if you apply for a visa in Canada or Mexico and your application is denied, you will not be allowed to re-enter the U.S. Discuss plans to apply for a visa in a country other than your own with one of the International Student Advisors.
The I-94 is a small white card issued by a U.S. Customs and Border Protection (CBP) inspector to record your immigration status. It indicates your Admission/Departure Number, personal information, date of entry, and length of authorized stay in the US. The notation "D/S" on your I-94 stands for "Duration of Status." It means that you may stay in the US as long as you are a full-time student making normal progress toward the specific educational objective (i.e., degree) indicated on your current I-20, until the date recorded on your current I-20.
Special care should be taken to keep this and all other immigration documents safe. If you lose your I-94, you must file an application for a replacement (Form I-102) along with the appropriate I-102 fee. Your I-94 is required for all official immigration and employment-related transactions, such as applying for employment benefits, or obtaining certification for travel or extensions.
An I-20 ("Certificate of Eligibility for Nonimmigrant [F-1] Student Status") is issued to a student who has been admitted to a full-time program of study and has provided evidence of the ability to finance his/her education and living costs while enrolled at Teachers College. For you to begin or continue your studies, you must have a valid I-20 issued by Teachers College for your current degree program.
Do not throw away an "old" I-20. All of your I-20's together are considered your "I-20-ID" and will be required by U.S. government agencies as proof of status. Keep all your I-20s together with your passport in a safe place. Keep a photocopy of each document in a separate safe place.
Page 3 of your I-20 is used to record curricular and optional practical training authorizations, reduced courseload authorizations, school transfers and other information. You are required to present your I-20, valid passport, and F-1 visa to the border official in order to be admitted to the US.
If you are going to change departments, are admitted to a new degree program, or need to extend your on-going program (beyond the completion of studies date on your current I-20), you will need a new I-20.