A document published by the Internal Revenue Service (IRS) that provides information on deducting home mortgage interest. Mortgage interest deductions are considered itemized deductions. IRS Publication 936 explains what can be deducted as mortgage interest, how to claim the deduction and limitations on the total amount that can be deducted. Types of mortgage interest that can be considered for the deduction include second mortgages, home equity loans and lines of credit.

In order to qualify for the deduction, the taxpayer must fill out Schedule A of Form 1040 and be legally liable for the mortgage. If the taxpayer is not legally liable for paying the mortgage, the mortgage interest cannot be deducted. The debt must also be secured debt.