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@Terry53029 wrote:

Section 280A has to do with disallowance of expenses  in connection with business use of home. It seems to me the daughter is just giving the parents a thank you gift for letting her use the families personal vacation home.

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I agree, 280A is a red herring (unless we circle back and start talking about expenses).  In terms of income, that's section 61.  "Except as otherwise provided in this subtitle, gross income means all income from whatever source derived."

The income is taxable income.