Common Misunderstandings About Mortgage Interest Deductions

The standard deduction — a flat amount the IRS allows all filers to subtract from income — was significantly increased by the Tax Cuts and Jobs Act of 2017. For many homeowners, especially those with smaller loans or lower interest rates, total itemized deductions no longer exceed the standard deduction threshold. That means the mortgage interest deduction provides no additional tax benefit for a large share of homeowners today.

Before assuming you'll itemize, tally up all potential itemized deductions — mortgage interest, state and local taxes (capped at $10,000), charitable contributions, and others — and compare the total to the current standard deduction for your filing status.

This is one of the most persistent misunderstandings. If you paid $10,000 in mortgage interest and fall in the 22% federal tax bracket, your deduction reduces your taxable income by $10,000 — saving you approximately $2,200 in taxes, not $10,000. A tax credit works dollar-for-dollar; a deduction does not.

The higher your marginal tax rate, the more a deduction is worth, which is why the benefit varies significantly among taxpayers.

Loans originated on or before December 15, 2017 are grandfathered under the older $1 million limit. For loans taken out after that date, only interest attributable to the first $750,000 of debt is deductible. If your mortgage balance exceeds that threshold, you can only deduct a proportional share of the interest paid.

This limit applies per household — not per mortgage — and encompasses combined debt on a primary and second home if both qualify. For more on core mortgage concepts, see mortgage terminology every homebuyer should know.

Mortgage interest on a rental or investment property is generally deducted on Schedule E as a rental expense, which offsets rental income. This is separate from the Schedule A itemized deduction for personal residences. The rules, limits, and interactions with passive activity rules differ substantially.

Mixed-use properties — such as a home you rent out part of the year — involve a more complex allocation calculation. A qualified tax professional can help determine how to correctly handle these situations.

When you refinance, you can typically still deduct the interest on the new loan — provided the balance does not exceed the applicable cap and the loan is secured by a qualified residence. However, if you take cash out during a refinance and use those funds for purposes other than buying, building, or substantially improving the home, that portion of interest may no longer qualify as deductible home acquisition debt.

Points paid to refinance (as opposed to an original purchase) are generally deducted over the life of the loan rather than all at once, unlike purchase-loan points which may be fully deductible in the year paid under certain conditions.