Buying your first home is expensive enough without leaving money on the table at tax time. For mortgages taken out after December 15, 2017, you can deduct interest on up to $750,000 of debt used to buy, build, or substantially improve your home — but only if you itemize your deductions rather than taking the standard deduction. That single choice determines whether the mortgage interest deduction actually saves you anything at all.
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This article is general information only and does not constitute professional advice. For your specific situation, consult a qualified professional.
These limits aren’t just numbers on a page — they decide how much of your monthly mortgage payment actually reduces your taxable income. The rules also differ depending on when you took out the loan, whether you’re married, and what you used the borrowed money for. Here’s what you actually need to know.
What First-Time Buyers Need to Know About Mortgage Interest Deductions
The central concept here is home acquisition debt — the IRS term for money borrowed to buy, build, or substantially improve a qualified home. Only interest on this type of debt qualifies for the deduction. A home equity line used to remodel a kitchen counts. The same line used to pay off credit cards does not.
What I tend to notice is that first-time buyers focus on the interest rate and monthly payment but rarely check whether their loan structure actually supports the deduction. A real estate lawyer can clarify how your specific loan terms interact with these rules before you close.
How the $750,000 Limit and Grandfathered Debt Affect Your Deduction
The mortgage interest deduction isn’t unlimited. For loans taken out after December 15, 2017, you can only deduct interest on the first $750,000 of home acquisition debt — $375,000 if you’re married and filing separately. Borrow $800,000 and the interest on the extra $50,000 is not deductible.
But there’s an important exception. If your mortgage was taken out before December 16, 2017, the old limit of $1 million ($500,000 for married filing separately) still applies. The IRS calls this grandfathered debt. Refinancing that old loan doesn’t automatically reset the limit — the refinanced debt keeps its original date and limit, as long as the new loan doesn’t exceed the amount refinanced.
What this means in practice: a couple buying a $900,000 home with a $720,000 mortgage is fully within the limit. A couple buying a $1.2 million home with a $960,000 mortgage exceeds it by $210,000. The interest on that excess portion is simply not deductible.
There’s also a separate cap on state and local tax deductions — including property tax — of $10,000 per year. Even if you pay $15,000 in property taxes, you can only deduct $10,000. That $10,000 cap is per return, not per property, so owning multiple homes doesn’t increase it.
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| Mortgage Date | Debt Limit (Joint) | Debt Limit (Separate) |
|---|---|---|
| Before Dec 16, 2017 | $1,000,000 | $500,000 |
| After Dec 15, 2017 | $750,000 | $375,000 |
| Refinanced grandfathered debt | Original limit retained | Original limit retained |
Worth weighing against these limits: if you’re buying in a high-cost area where mortgages routinely exceed $750,000, the deduction is partial at best. The pros and cons of buying off-plan often include different financing structures that can affect how much debt qualifies.
Common Mistakes First-Time Buyers Make With Mortgage Interest Deductions
Assuming the deduction applies automatically
Many first-time buyers think owning a home means they automatically deduct mortgage interest. That’s not how it works. You only benefit if you itemize deductions on Schedule A — and the standard deduction for a single filer in 2024 is $14,600. If your total itemized deductions (mortgage interest, property taxes, charitable gifts, etc.) don’t exceed that, itemizing does nothing. For a first home with a $250,000 mortgage at 6%, you’d pay roughly $15,000 in interest the first year. Add $5,000 in property taxes and you’re at $20,000 — enough to itemize. But a $150,000 mortgage at the same rate produces only $9,000 in interest, and with $3,000 in taxes you’re at $12,000 — below the standard deduction.
Using home equity proceeds for non-qualifying expenses
This is the most expensive mistake I see. A homeowner takes out a $50,000 home equity loan, uses $20,000 for a kitchen renovation and $30,000 to pay off credit cards. Only the interest on the $20,000 used for the renovation is deductible. The IRS traces the use of the proceeds, not the loan itself. Keep separate accounts if you’re mixing qualifying and non-qualifying uses. A finance professional can help you structure the loan to maximise the deductible portion.
Misreporting points paid at closing
Points are prepaid interest, and the general rule is that you deduct them ratably over the life of the loan. But for a mortgage used to buy your main home, you can deduct the full amount in the year you pay them — provided certain conditions are met. The loan must be secured by your main home, paying points must be an established business practice in your area, and the points can’t exceed what’s generally charged. Sellers can also pay points on your behalf, and you can deduct those as if you paid them yourself. The key is that the points must be clearly shown on your settlement statement as points, not as fees for services like appraisals or title searches.
Ignoring the impact of refinancing
Refinancing resets the clock on your mortgage, but it doesn’t automatically reset your deduction limits. If you refinance grandfathered debt, the new loan keeps the old limit — as long as the new loan doesn’t exceed the principal balance of the old one. But if you take cash out during refinancing, that extra cash is treated as a new mortgage and subject to the $750,000 limit. The interest on the cash-out portion is only deductible if you use it to substantially improve the home. A business lawyer can review refinancing documents to flag these issues before you sign.
How to Calculate and Claim Your Mortgage Interest Deduction
Determining your deductible interest amount
The IRS gives you two methods to figure deductible interest. The simplest: use the mortgage interest statement your lender sends you — Form 1098 — which shows the total interest you paid during the year. If your mortgage balance never exceeded the applicable limit ($750,000 or $1 million), you can deduct the full amount shown on Form 1098. If your balance exceeded the limit, you need to calculate the deductible portion using the average mortgage balance method. Add the balance at the start of the year to the balance at the end, divide by two, then multiply the interest paid by the ratio of the limit to that average balance.
Reporting on your tax return
You report the deduction on Schedule A (Form 1040), line 8a for mortgage interest and points reported on Form 1098, and line 8b for mortgage interest not reported on Form 1098. If you paid points that qualify for immediate deduction, report those on line 8c. The total flows to line 8e. You’ll also report deductible mortgage insurance premiums on line 8d — but note that the deduction for mortgage insurance premiums has expired under current law, so check the latest IRS guidance before claiming it.
Handling mixed-use mortgages
A mixed-use mortgage is one where part of the proceeds went to buy the home and part went to something else — like a home equity line used partly for improvements and partly for other expenses. You need to track the qualifying and non-qualifying portions separately. The IRS allows you to treat the loan as two separate debts: one for acquisition debt and one for non-deductible debt. Your lender won’t do this for you — you have to maintain your own records showing how each dollar was spent.
Upcoming changes and what to watch for
The Tax Cuts and Jobs Act limits on mortgage interest deductions are scheduled to sunset after 2025. If Congress doesn’t extend them, the limits could revert to pre-2018 rules — $1 million for acquisition debt and no cap on home equity loan interest deductions. That would be a significant change for homeowners in high-cost markets. For now, plan under the current rules, but keep an eye on legislative developments. The deed restrictions on UK properties operate differently, but the principle of tracking what your borrowed money actually pays for is the same.
Frequently Asked Questions
Can I deduct mortgage interest on a second home? ▾
What if I’m married but only one spouse is on the mortgage? ▾
Can I deduct mortgage interest if I use part of my home as an office? ▾
What happens to the deduction if I sell my home mid-year? ▾
Do I need to keep receipts for home improvements to support the deduction? ▾
Can I deduct points paid by the seller? ▾
The Bottom Line on Mortgage Interest Deductions for First-Time Buyers
The mortgage interest deduction is real, but it’s not automatic and it’s not unlimited. For most first-time buyers with mortgages under $300,000, the standard deduction will likely be larger than what you’d get from itemizing — meaning the deduction provides no benefit at all. The real value comes when your mortgage is large enough, or your other deductible expenses are high enough, to push you past the standard deduction threshold. That’s when every dollar of mortgage interest starts reducing your taxable income.
Remember: this article is general information only. For advice on your specific situation, speak to a qualified professional.
If this was useful, you might also want to read how to avoid hidden pitfalls in leasehold purchases.
Sources and Further Reading
Renovation Rescue: Buying a Fixer-Upper in the UK — If you’re considering a home that needs work, this guide covers the costs and trade-offs of buying a property that requires substantial improvement.
IRS (2024). Publication 936: Home Mortgage Interest Deduction. 🔗
National Tax Reports (2024). Tax Deductions on Buying a House. 🔗
