You can deduct your home mortgage interest only if your mortgage is a secured debt. A secured debt is one in which you sign an instrument (such as a mortgage, deed of trust, or land contract) that:

• Makes your ownership in a qualified home security for payment of the debt,
• Provides, in case of default, that your home could satisfy the debt, and
• Is recorded or is otherwise perfected under any state or local law that applies.

In other words, your mortgage is a secured debt if you put your home up as collateral to protect the interests of the lender.

Per IRS Publication 936 Home Mortgage Interest Deduction, page 4:

Choice to treat the debt as not secured by your home. You can choose to treat any debt secured by your qualified home as not secured by the home. This treatment begins with the tax year for which you make the choice and continues for all later tax years. You can revoke your choice only with the consent of the IRS.

You may want to treat a debt as not secured by your home if the interest on that debt is fully deductible (for example, as a business expense) whether or not it qualifies as home mortgage interest. This may allow you, if the limits in Part II apply, more of a deduction for interest on other debts that are deductible only as home mortgage interest.

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