Most or all of your mortgage interest can be deductible, but only if you itemize deductions and only on qualifying “home acquisition debt” up to IRS limits (generally $750,000 of debt for most recent mortgages).

Quick Scoop

  • For U.S. federal taxes, you can deduct interest on up to $750,000 of qualifying home acquisition debt if you’re single or married filing jointly, or $375,000 if married filing separately.
  • “Home acquisition debt” means a loan secured by your home where the money was used to buy, build, or substantially improve your main home or one second home you personally use.
  • If your total mortgage balance is at or below those limits and the loan is qualifying, then 100% of the interest you pay for the year is generally deductible, as long as you itemize instead of taking the standard deduction.

When interest is fully deductible

Your mortgage interest is usually fully deductible if:

  • All of your home loans are secured by your main home or one second home.
  • The loan proceeds were all used to buy, build, or improve those homes (not to pay off credit cards, invest, etc.).
  • Your total qualifying mortgage balance never exceeds $750,000 ($375,000 MFS), or the higher $1,000,000/$500,000 “grandfathered” limits for certain pre‑Dec. 16, 2017 loans.

If you meet those conditions and you itemize, all of the interest shown on Form 1098 from those loans is normally deductible.

When only part is deductible

Only a portion of your mortgage interest is deductible if:

  • Your total qualifying mortgage debt exceeds the limit (for most newer loans, over $750,000).
  • Part of the loan was used for non‑housing purposes (like debt consolidation or tuition), in which case interest tied to that part is not deductible.

In that case, you:

  1. Figure the percentage of your average mortgage balance that is at or under the IRS limit (for example, $750,000 ÷ $900,000).
  1. Multiply that percentage by your total mortgage interest paid to get the deductible portion.

Tax software and IRS Publication 936 offer worksheets to do this fraction for you.

Other key conditions

  • You must itemize deductions on Schedule A; if the standard deduction is larger than your itemized deductions, you get no benefit from the mortgage interest deduction that year.
  • Interest on home equity loans or HELOCs is deductible only if the money was used to buy, build, or substantially improve the home that secures the loan.
  • The rules above apply separately to U.S. federal tax; other countries (or even states) can have very different rules on how much of your mortgage interest is tax deductible.

Bottom line: if your mortgage is within the IRS limits and was used entirely for your home, all of the interest is generally deductible if you itemize; once you exceed the limits or use funds for non‑home purposes, only a pro‑rated slice of that interest is deductible.

Information gathered from public forums or data available on the internet and portrayed here.