Fully deductible interest: Home Mortgage Interest Deductions (2025 IRS Guide)

This guide covers “Fully deductible interest” within home mortgage interest deductions. The following material presents the IRS treatment of this topic, including the qualifications, exceptions, and examples in the source section. Read the rules alongside the facts of your own situation before deciding what to report, deduct, or document.

Adapted from Publication 936 (2025), Home Mortgage Interest Deduction, published by the Internal Revenue Service. This guide retains the source edition’s years, amounts, deadlines, and examples. It is guidance for that edition, not a statement that the same figures apply to every tax year.

Context for these rules

This part explains what you can deduct as home mortgage interest. It includes discussions on points and how to report deductible interest on your tax return.

Generally, home mortgage interest is any interest you pay on a loan secured by your home (main home or a second home). The loan may be a mortgage to buy your home, or a second mortgage.

You can’t deduct home mortgage interest unless the following conditions are met.

• You file Form 1040 or 1040-SR and itemize deductions on Schedule A (Form 1040).

• The mortgage is a secured debt on a qualified home in which you have an ownership interest. Secured Debt and Qualified Home are explained later.

Fully deductible interest

Fully deductible interest.

In most cases, you can deduct all of your home mortgage interest. How much you can deduct depends on the date of the mortgage, the amount of the mortgage, and how you use the mortgage proceeds.

If all of your mortgages fit into one or more of the following three categories at all times during the year, you can deduct all of the interest on those mortgages. (If any one mortgage fits into more than one category, add the debt that fits in each category to your other debt in the same category.) If one or more of your mortgages doesn’t fit into any of these categories, use Part II of this publication to figure the amount of interest you can deduct.

The three categories are as follows.

1. Mortgages you took out on or before October 13, 1987 (called grandfathered debt).

2. Mortgages you (or your spouse if married filing a joint return) took out after October 13, 1987, and prior to December 16, 2017 (see binding contract exception below), to buy, build, or substantially improve your home (called home acquisition debt), but only if throughout 2025 these mortgages plus any grandfathered debt totaled $1 million or less ($500,000 or less if married filing separately).

   Exception. A taxpayer who enters into a written binding contract before December 15, 2017, to close on the purchase of a principal residence before January 1, 2018, and who purchases such residence before April 1, 2018, is considered to have incurred the home acquisition debt prior to December 16, 2017.

3. Mortgages you (or your spouse if married filing a joint return) took out after December 15, 2017, to buy, build, or substantially improve your home (called home acquisition debt), but only if throughout 2025 these mortgages plus any grandfathered debt totaled $750,000 or less ($375,000 or less if married filing separately).

The dollar limits for the second and third categories apply to the combined mortgages on your main home and second home.

See Part II for more detailed definitions of grandfathered debt and home acquisition debt.

You can use Figure A to check whether your home mortgage interest is fully deductible.

Figure A. Is My Home Mortgage Interest Fully Deductible?

Figure A. Is My Home Mortgage Interest Fully Deductible?

Summary: This flowchart is used to determine if the taxpayer's home mortgage interest is fully deductible.

Start Here

Decision (1)

Do you meet the conditions (Footnote 1) to deduct home mortgage interest?

Footnote 1: You must itemize deductions on Schedule A (Form 1040). The loan must be a secured debt on a qualified home. See Part I, Home Mortgage Interest, earlier.

• If no, you can't deduct the interest payments as home mortgage interest (Footnote 2). Footnote 2: See Table 2 in Part II of this publication for where to deduct other types of interest payments. Stop here
• If yes, continue to Decision (2)

Decision (2)

Were all of your home mortgages taken out on or before October 13, 1987?

• If yes, your home mortgage interest is fully deductible. You don’t need to read part II of this publication. Stop here.
• If no, continue to Decision (3)

Decision (3)

Were all of your home mortgages taken out after October 13, 1987, used to buy, build or substantially improve the main home secured by that main home mortgage or used to buy, build or improve the second home secured by that second home mortgage, or both?

• If no, go to part II of this publication to determine the limits on your deductible home mortgage interest.
• If yes, continue to Decision (4)

Decision (4)

Were your (or your spouse’s if married filing a joint return) mortgage balances $750,000 or less ($375,000 or less if married filing separately) (or $1 million or less ($500,000 if married filing separately) if all the debt was incurred prior to December 16, 2017) at all times during the year (Footnote 3)?

Footnote 3: A taxpayer who enters into a written binding contract before December 15, 2017, to close on the purchase of a principal residence before January 1, 2018, and who purchases such residence before April 1, 2018, is considered to have incurred the home acquisition debt prior to December 16, 2017, and may use the 2017 threshold amounts of $1,000,000 ($500,000 for married filing separate).

• If yes, your home mortgage interest is fully deductible. You don’t need to read part II of this publication. Stop here.
• If no, continue to Decision (5)

Decision (5)

Were your (or your spouse’s if married filing a joint return) grandfathered debt plus home acquisition debt balances $750,000 or less (Footnote 4) ($375,000 or less if married filing separately) (or $1 million or less ($500,000 if married filing separately) if all the debt was incurred prior to December 16, 2017) at all times during the year (Footnote 3)?

Footnote 4: See Part II of this publication for more information about grandfathered debt and home acquisition debt.

Footnote 3: A taxpayer who enters into a written binding contract before December 15, 2017, to close on the purchase of a principal residence before January 1, 2018, and who purchases such residence before April 1, 2018, is considered to have incurred the home acquisition debt prior to December 16, 2017, and may use the 2017 threshold amounts of $1,000,000 ($500,000 for married filing separately).

• If yes, your home mortgage interest is fully deductible. You don’t need to read part II of this publication. Stop here.
• If no, go to part II of this publication to determine the limits on your deductible home mortgage interest.

Using the guidance

Keep the documents that establish the dates, amounts, and circumstances described above. References to other chapters, forms, worksheets, or earlier and later sections refer to the linked IRS publication. Check the full publication and its updates before relying on a rule for a different tax year or a situation not addressed here.

Sources and further reading

• Publication 936 (2025), Home Mortgage Interest Deduction: Home Mortgage Interest — Fully deductible interest — Internal Revenue Service; 2025 edition.

The cited U.S. government text is in the public domain. Source accessed October 28, 2026. Fynoptic has organized this material for educational use and is independent of, and not endorsed by, the IRS.