Is mortgage interest tax deductible?

Yes, on up to $750K of mortgage debt for primary and second homes (post-2017 mortgages). Itemize on Schedule A. Most homeowners no longer itemize due to the higher standard deduction.

Mortgage interest is deductible as an itemized deduction on Schedule A, subject to limits. Current rules (post Tax Cuts and Jobs Act, mortgages originated after Dec 15, 2017): you can deduct interest on up to $750,000 of "acquisition indebtedness" - mortgage debt used to buy, build, or substantially improve a primary residence and one second home (combined limit). Mortgages originated before Dec 16, 2017 are grandfathered at the old $1M limit. To deduct mortgage interest you must itemize on Schedule A. The 2024 standard deduction is $14,600 single / $29,200 married filing jointly. Most homeowners with mortgages under $400K and standard property tax/state tax burden don't itemize - they take the standard deduction instead. The "SALT cap" ($10K limit on state and local tax deduction) reduces itemizing benefit further for high-tax-state homeowners. Home equity loan interest is deductible only if the funds were used to buy, build, or substantially improve the home that secures the loan. HELOC for personal use, debt consolidation, or anything other than home improvement is NOT deductible. Investment property mortgage interest is fully deductible on Schedule E without the $750K cap, because it is a business expense rather than itemized personal deduction.