The Immigration and Naturalization Service (INS) requires these forms for entry to the United States. Please read the I-20 carefully before you apply for your visa form. Prior to any departure from the United States (even a weekend trip to Canada), your form must have been signed in the previous 12 months by the International Student Advisor. Calling the International Student Advisor for a signature at the last minute is not a problem. In the case that a signature is forgotten, International Students are usually given a lengthy question-and-answer session at the entry port and then given a form for the International Student Advisor to sign and return to INS within 30 days.