Only the person that actually paid the interest can deduct it. You can strategize at the beginning of the year who is going to make the payments and then deduct the interest, but you can't strategize at the end of the year.
and only those that are on the mortgage are eligible to deduct the interest.
first line of the "answer" from this FAQ:
"To deduct taxes or interest on Schedule A (Form 1040), Itemized Deductions, you generally must be legally obligated to pay the expense and must have paid the expense during the year."
https://www.irs.gov/faqs/itemized-deductions-standard-deduction/other-deduction-questions/other-dedu...
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