You cannot deduct the mortgage interest and property tax if your name is not on the loan or the deed.
However, you might be able to claim your partner as a dependent on your return if he meets the requirements of Qualifying relative.
Qualifying relative
• They don't have to be related to you (despite the name).
• They aren't claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They lived with you the entire year.
• They made less than $4,300 in 2020. (Social Security does not count)
• You provided more than half of their financial support.
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