The student loan interest deduction is found on line 33 of your federal Form 1040 or Line 18 of Form 1040A.
To calculate your California deduction, take your student loan interest deduction from the 1040 and divide it by the number of months you paid interest last year. Then multiply it by the number of those months that you lived in California. For example, if you paid interest all year and lived in California for 5 months, then you would multiply the interest by 5/12. If you weren't paying the loan while you lived in California, then the California student loan deduction would be $0.
Note that the maximum allowable student loan interest deduction on the 1040 is $2,500.
