The IRS does not allow a taxpayer to claim an interest deduction if it is a personal loan (This includes a personal car loan.)
If however, the loan is a home equity loan, you may be able to claim this as an itemized deduction on Schedule A.
If this is student loan interest, you would be able to claim this on your tax return if you meet all the eligibility requirements. (Student loan interest would be reported to you on a Form 1098-E).
