Why Your Mortgage Interest Deduction Is Probably Worth $0

"At least you'll get the tax deduction." It's one of the most common things people hear when they're thinking about buying a house. The mortgage interest deduction has been a selling point for homeownership for decades. And it used to be a pretty good one.

But the 2017 Tax Cuts and Jobs Act changed the math for most people. Here's what actually happens when you sit down to do your taxes as a homeowner.

How the deduction actually works

When you pay mortgage interest, that interest is tax-deductible. But there are two catches that many people don't understand until it's too late.

Catch #1: You have to itemize. You can either take the standard deduction or add up all your itemized deductions (mortgage interest, state/local taxes, charitable giving, etc.) and take whichever is larger. You don't get both. So the mortgage interest deduction only helps you if your total itemized deductions exceed the standard deduction.

Catch #2: Only the amount above the standard deduction matters. If your itemized deductions total $18,000 and the standard deduction is $15,000, your actual tax benefit is on the $3,000 difference, not the full $18,000. At a 24% marginal rate, that's $720 in savings. Not the thousands most people imagine.

The standard deduction problem

The standard deduction in 2026 is approximately $15,000 for single filers and $30,000 for married couples filing jointly. These numbers are significantly higher than they were before 2018.

This means your mortgage interest plus state taxes plus all other itemized deductions need to clear a high bar before you see any tax benefit at all. For married couples, that bar is $30,000. That's a lot of deductions.

The SALT cap makes it worse

State and local tax (SALT) deductions are capped at $40,000 for most filers in 2026 (phased down for incomes above $500,000). Before the cap, homeowners in high-tax states could deduct their entire property tax bill plus state income taxes. Now there's a ceiling.

This matters because property taxes were a big part of the itemized deduction math for many homeowners. If you live in New Jersey and pay $12,000 in property tax and $8,000 in state income tax, your SALT deduction is $20,000. Combined with mortgage interest, that might push you above the standard deduction. But in lower-tax states, the SALT component is much smaller, making it harder to itemize.

A worked example: $500,000 home, single filer, 24% bracket

Let's walk through the math for a real scenario.

That's a real savings. But notice what's happening. You had to pay $25,800 in mortgage interest to save $5,592 in taxes. You didn't "make money" on the deduction. You spent $25,800 and got $5,592 back. The net cost of that interest was still $20,208.

And this is a favorable scenario. A $500,000 home with a $400,000 loan at 6.5%. Smaller loans, lower rates, or states with low property taxes often don't clear the standard deduction at all.

When the deduction is worth $0

Let's look at a more common scenario.

This couple gets absolutely no tax benefit from their mortgage. They'd take the standard deduction whether they owned or rented. The mortgage interest deduction is worth exactly $0 to them.

This is not an edge case. According to IRS data, roughly 90% of tax filers take the standard deduction. The mortgage interest deduction is meaningless for the vast majority of homeowners.

How the deduction shrinks over time

Even if you do benefit from itemizing in year one, the benefit gets smaller every year. As you pay down your mortgage, the interest portion of each payment drops. In year 5, you're paying less interest than in year 1. In year 10, even less. Eventually, your itemized deductions fall below the standard deduction and the benefit disappears entirely.

So the mortgage interest deduction is at best a temporary, partial offset to a large unrecoverable cost. It's not a reason to buy a home.

How to check your real number

Don't guess. Add up your actual deductions:

• Year 1 mortgage interest (your lender will tell you, or multiply your loan amount by roughly your rate)
• Property taxes
• State income taxes (remember the SALT cap)
• Charitable donations
• Any other itemized deductions

If the total exceeds your standard deduction ($15,000 single, $30,000 married), multiply the difference by your marginal tax rate. That's your actual annual tax savings from owning. For most people, it's either zero or much smaller than they expected.

Our rent vs. buy calculator does this math automatically. It compares your standard deduction against itemized, applies the SALT cap, and only counts the incremental benefit. No guessing required.