Can I deduct mortgage interest on my state tax return?

It depends on your state. Most states with an income tax conform to federal itemized deductions, which includes mortgage interest. But some states — like Pennsylvania and Illinois — don't allow itemized deductions at all. And nine states have no income tax, so the federal deduction is the only one available.

Does the $750,000 federal debt limit apply to state deductions too?

For states that conform to federal rules, yes — the same $750,000 limit applies. States with their own deduction rules (like Massachusetts) may have different limits. Check your state's department of revenue for specifics.

How does the SALT cap affect my mortgage interest deduction?

The $10,000 SALT cap limits your combined deduction for state and local taxes (including property taxes and state income tax). It doesn't directly cap mortgage interest, but it affects whether itemizing is worth it. In high-tax states, the SALT cap reduces the other itemized deductions you can claim alongside mortgage interest.

Which states offer the biggest combined federal and state benefit?

California, New York, and New Jersey offer the largest combined benefit because they have both high state income tax rates and conform to federal itemized deductions. A California homeowner in the 9.3% state bracket plus 22% federal gets a ~31% effective rate on every dollar of deductible mortgage interest.

Mortgage Interest Deduction by State

The federal mortgage interest deduction gets most of the attention — and for good reason. But if you live in a state with income tax, your state return matters too. The rules vary more than most people realize.

The Federal Baseline

At the federal level, you can deduct mortgage interest on debt up to $750,000 (for loans originated after December 15, 2017). That covers your primary home and one second home. Pre-2018 loans get the older $1 million limit. The full rules are in IRS Publication 936.

To claim it, you itemize on Schedule A. Given the 2025 standard deduction ($30,000 for married joint filers), this only makes sense if your total itemized deductions exceed that threshold.

How States Handle It

States fall into three buckets:

No income tax — the federal deduction is the only deduction there is. Texas, Florida, Washington, Tennessee, Nevada, Wyoming, South Dakota, and Alaska fall here.
Conforms to federal — your state return piggybacks on the federal itemized deductions, including mortgage interest. Most states work this way.
Doesn't conform — the state has its own rules. Pennsylvania, for example, doesn't allow itemized deductions at all. Massachusetts uses a hybrid approach.

State-by-State Breakdown

State	Deductible at State Level?	Notes
California	✅ Yes	Follows federal rules. No additional state deduction, but no cap reduction either.
New York	✅ Yes	Conforms to federal. NYC residents may also deduct on city returns.
Texas	— No income tax	No state income tax — federal deduction is your only option.
Florida	— No income tax	No state income tax.
Illinois	❌ Limited or no	Flat 4.95% state tax but doesn't allow itemized deductions. Standard deduction only.
Pennsylvania	❌ Limited or no	Doesn't conform to federal itemized deductions at all. Mortgage interest not deductible at state level.
New Jersey	✅ Yes	Conforms to federal for state income tax purposes.
Ohio	✅ Yes	Generally conforms to federal itemized deductions.
Georgia	✅ Yes	Follows federal itemized deductions.
Washington	— No income tax	No state income tax.
Arizona	✅ Yes	Conforms to federal rules.
Massachusetts	❌ Limited or no	Allows mortgage interest deduction but uses its own calculation — not full federal conformity.
Colorado	✅ Yes	Conforms to federal itemized deductions.
Minnesota	✅ Yes	Allows its own mortgage interest credit for lower-income filers as an alternative.
Tennessee	— No income tax	No state income tax (phased out fully in 2021).

Tax laws change — verify with your state revenue department or a CPA.

The States Where This Matters Most

California: With a top marginal rate of 13.3%, itemizing on your state return can save serious money. California conforms to federal rules, so if you itemize federally, you itemize in California too.

New York: High earners in New York City get a double benefit — the deduction works on both the state and city returns.

Pennsylvania: Uses a flat 3.07% rate but doesn't allow itemized deductions at all. Your mortgage interest isn't deductible at the state level, full stop.

Illinois: Flat 4.95% tax but uses its own standard deduction system — no itemization. Federal deductions don't carry over.

Don't Forget the $10,000 SALT Cap

The $10,000 cap on state and local tax (SALT) deductions affects whether itemizing even makes sense. Before 2018, you could deduct all your property taxes and state income taxes. Now you're limited to $10,000 total. In high-tax states, that cap often erodes the benefit of itemizing. See the IRS overview on SALT deductions.

How to Calculate Your State Benefit

If you paid $18,000 in mortgage interest last year and your state income tax rate is 6%, your state tax savings would be roughly $1,080. Add your federal savings (22% bracket: $3,960), and your combined benefit is about $5,040 — that's the number that matters, not the deduction itself.