Mortgage Interest Deduction
The mortgage interest deduction is the federal income tax benefit most associated with homeownership — and since the Tax Cuts and Jobs Act of 2017 dramatically raised the standard deduction, it now benefits far fewer households than it once did. Today, roughly 87% of taxpayers claim the standard deduction rather than itemizing, meaning most homeowners never actually deduct mortgage interest. For the approximately 13% who do itemize, the deduction applies to interest paid on acquisition debt — mortgage debt used to buy, build, or substantially improve a qualified residence — up to a $750,000 debt cap for loans originated after December 15, 2017. Mortgages originated before that date are grandfathered under the older $1,000,000 cap. Home equity loan or HELOC interest is not deductible unless the proceeds were actually used to buy, build, or substantially improve the home — a rule change that caught many homeowners off guard after 2017. The deduction covers a primary home plus one second home. At current mortgage rates, a $750,000 loan generating over $40,000 in annual interest can still make itemizing worthwhile — but the math depends entirely on whether your total itemized deductions clear the standard deduction threshold.
Current Law (2026)
Taxpayers who itemize can deduct interest paid on mortgage debt used to acquire, build, or substantially improve a qualified residence.
| Parameter | 2026 Current Law | Pre-2018 Law |
|---|---|---|
| Acquisition debt limit | $750,000 | $1,000,000 |
| MFS debt limit | $375,000 | $500,000 |
| Home equity debt interest | Not deductible (unless used for home improvement) | Deductible on up to $100,000 |
| Qualifying properties | Primary + 1 second home | Same |
Key Numbers
- 87% of taxpayers claim the standard deduction — meaning 87% get zero benefit from the mortgage interest deduction regardless of whether they own a home and pay mortgage interest; only the ~13% who itemize gain anything from this provision
- $750,000 acquisition debt cap for mortgages originated after December 15, 2017 — made permanent by the One Big Beautiful Bill Act (2025); $1,000,000 cap grandfathered for mortgages originated on or before December 15, 2017
- At 7% on a $600,000 mortgage: first-year interest ≈ $42,000 — easily exceeding the standard deduction when combined with property taxes; at the 24% bracket, that deduction saves approximately $10,000 in federal tax; at the 22% bracket, approximately $9,200
- $32,200 standard deduction for married filing jointly in 2026 — a HELOC with $8,000 in interest and a $300,000 mortgage at 6.5% ($19,500 interest) produces roughly $27,500 in mortgage interest alone; to itemize, you'd need that mortgage interest plus property taxes, state income tax (capped at $10,000 SALT), and charitable giving to clear $32,200
- Points on purchase: mortgage origination points paid at purchase are deductible in full in the year paid if they meet IRS criteria (common at closing); points on a refinance must be amortized over the loan life — a meaningful difference at closing on a home purchase
- $10,000 SALT cap interacts directly with the mortgage interest decision: homeowners in high-tax states (NY, NJ, CA, CT) with large property tax bills often hit the SALT cap alone and can add mortgage interest on top, making itemizing worthwhile; homeowners in low-tax states may find standard deduction still wins even with significant mortgage interest
- Pre-TCJA share of itemizers: approximately 30% of taxpayers itemized before 2018; after TCJA raised the standard deduction, that fell to approximately 13%; the OBBB permanent extension means this lower share is now the long-term baseline, not a temporary condition
Legal Authority
- 26 U.S.C. § 163 — Interest
- IRC Section 163(h) — Qualified residence interest
- IRC Section 163(h)(3) — Acquisition indebtedness definition and limits
How It Works
The deduction applies only to acquisition indebtedness — debt used to buy, build, or substantially improve the home (IRC § 163(h)(3)). Interest on home equity debt used for other purposes (debt consolidation, tuition, a car, or a vacation) is not deductible under current law — a rule change from pre-TCJA law that caught many borrowers off guard after 2017. A HELOC used for a kitchen remodel qualifies; the same HELOC used for credit card payoff does not. If a HELOC serves both qualified and non-qualified purposes, interest must be allocated proportionally between deductible and non-deductible use.
The debt cap depends on when the mortgage originated. Loans originated on or before December 15, 2017 are grandfathered at $1,000,000 ($500,000 for married filing separately) — a benefit preserved permanently by the One Big Beautiful Bill Act (2025). New loans originated after December 15, 2017 face the $750,000 cap ($375,000 for MFS). Refinancing preserves grandfathered status up to the original outstanding principal balance — refinancing at the same or lower amount doesn't forfeit the $1M cap, but a cash-out refinance above the original principal subjects only the original amount to the higher cap.
The deduction covers a primary residence plus one second home. If you own three or more properties, you choose which two to designate as qualifying residences — and the designation can be changed from year to year, which matters when a vacation home becomes a primary residence or moves to rental use (rental-property mortgage interest is deducted on Schedule E, not Schedule A, without the personal debt cap). The deduction requires itemizing on Schedule A, which means your total itemized deductions must exceed the standard deduction ($32,200 for married filing jointly in 2026) — the reason 87% of homeowners get zero benefit from mortgage interest regardless of how much they pay. Points paid on a purchase mortgage are deductible in full in the year paid; points on a refinance must be amortized over the life of the loan — a meaningful distinction at closing. Unlike many other itemized deductions, mortgage interest on acquisition debt is fully allowed under the Alternative Minimum Tax, making it one of the most AMT-stable deductions available to high-income itemizers.
How It Affects You
The mortgage interest deduction only benefits you if your total itemized deductions exceed the standard deduction. For a married couple with a $300,000 mortgage at 6.5% (~$19,500 annual interest), they need at least $12,700 more in other itemized deductions (SALT, charitable, etc.) to exceed the $32,200 standard deduction. In practice, this means the deduction primarily benefits homeowners with large mortgages, high property taxes, or significant charitable giving.
If you have a large new mortgage at today's rates: A new $600,000 mortgage at 7% generates roughly $42,000 in first-year interest — easily exceeding the standard deduction when combined with even modest property taxes and state income tax. For these borrowers, itemizing provides real tax savings: at the 24% bracket, $42,000 of deductible interest saves roughly $10,000 in federal tax. The deduction doesn't make a $600K mortgage cheap, but it reduces the after-tax cost meaningfully.
If you have a pre-2018 mortgage: Your grandfather status (allowing interest deduction on up to $1M of acquisition debt) is preserved as long as you don't refinance into a higher principal. Refinancing to a lower rate or shorter term preserves the grandfathered limit up to your original principal balance. If you cash-out refinance above the original principal, only the original amount is grandfathered — the additional amount is subject to the $750K limit.
If you used a HELOC for non-home purposes: Interest on home equity debt used for anything other than buying, building, or substantially improving the home is not deductible under current law. This includes HELOCs used for debt consolidation, college tuition, or vehicles. The same HELOC used for a kitchen renovation is deductible; used for a car payment, it's not. If your HELOC serves both purposes, you'll need to allocate interest between deductible and non-deductible uses.
If you're on the itemizing margin: Many households near the standard deduction threshold can "bunch" deductions — making two years' worth of charitable contributions in a single year, or timing certain payments — to itemize in alternating years. This strategy extracts value from mortgage interest in years you itemize while taking the standard deduction in other years.
State Variations
Most states with an income tax that allow itemized deductions also allow mortgage interest, but some differ:
- CA: Conforms to the $1,000,000 pre-TCJA limit (more generous than federal)
- NY: Conforms to the $1,000,000 pre-TCJA limit
- NJ: Allows mortgage interest deduction
- IL: No itemized deductions (flat tax state with no personal deductions)
- States with no income tax: N/A
Implementing Regulations
- 26 CFR Part 1 — Income tax regulations (section 1.163-10T: qualified residence interest rules (temporary); section 1.6050H-1: information reporting of mortgage interest received)
Pending Legislation (119th Congress)
- HR 918 (Rep. Brownley, D-CA) — Mortgage Insurance Tax Deduction Act of 2025. Would make the mortgage insurance premium tax deduction permanent for premiums paid or accrued after Dec. 31, 2024, letting homeowners continue to deduct those costs. Status: Introduced.
Recent Developments
The One Big Beautiful Bill Act (2025) made the mortgage interest deduction's current structure permanent law. The $750,000 acquisition debt cap — previously set to expire after 2025 as a TCJA provision — is now permanent. So is the disallowance of home equity interest for non-home-improvement uses. The practical effect: the pre-2018 world where a HELOC used for anything (debt consolidation, vacation, tuition) generated deductible interest is definitively gone for new borrowers. For the roughly 13% of taxpayers who still itemize, the deduction framework is now stable and unlikely to change in the near term barring major tax legislation — which means the planning questions shift to whether your specific loan and financial situation makes itemizing worthwhile, rather than whether the rules might change under you.
Mortgage insurance premiums (PMI) are deductible again for tax years starting after 2025. The PMI deduction — available to itemizers with adjusted gross income below $109,000 ($54,500 MFS), phasing out between $100,000 and $109,000 — had repeatedly lapsed and been retroactively renewed by Congress over the past decade. It was allowed to expire after 2021 and was not extended for 2022-2024. The OBBB Act's permanent extension gives homeowners with PMI a stable deduction they can plan around — worth approximately $500–$1,500 in deductible interest annually for a typical FHA or conventional loan with private mortgage insurance. For first-time buyers putting less than 20% down, this is real money. See PMI Requirements for how PMI cancellation rules interact.
The "mortgage lock-in effect" — where homeowners who refinanced at 2.5-3.5% rates during 2020-2021 are unwilling to sell because any replacement mortgage would carry a 6.5-7% rate — has an underappreciated interaction with the mortgage interest deduction. Homeowners in 2020-era mortgages have far lower annual interest than their 2026 equivalents: a $500,000 mortgage at 3% generates roughly $15,000 in first-year interest vs. roughly $35,000 at 7%. At $15,000 in mortgage interest, most of those homeowners can't clear the standard deduction threshold on mortgage interest alone without substantial property taxes or other deductions — meaning the deduction has little or no value to them. Meanwhile, new buyers at 7% rates are much more likely to be itemizing and actually benefiting from the deduction. This creates the unusual situation where the deduction benefits are currently concentrated among recent buyers who took on high-rate loans, while the long-term homeowners who dominate housing stock often get no benefit because their rates are so low.