If an instructor permits a student to take a class on an “Audit” basis, the student is required to be officially enrolled in the class and submit a Credit/No Credit/Audit option form(PDF) by last day to add of each semester (check Registration Calendar for exact date).
"AU" - Auditing a Class
An auditor must be officially enrolled in the course. Enrollment as an auditor is subject to permission of the instructor provided there is space available in the course. Auditors are subject to the same fee structure as credit students and regular class attendance is expected. Once enrolled as an auditor, a student may not change to credit status unless such a change is requested no later than the last day to add classes in that term. A student who is enrolled for credit may not change to audit after the last day to add classes in that term.
Note: The above information was taken from SJSU Catalog, to view if there is any update information, please follow this navigation : SJSU Policies and Procedures : Undergraduate Information and Requirements : Grading System for Undergraduate : "AU" - Auditing a Class.