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Good evening. If his only income was from Social Security, those benefits are not taxable. SS benefits are only taxable if you excess certain minimum levels of other taxable income
. If there is no other taxable income, the SS benefits are not taxable.
With regard to the sale of the house, if you sold it prior to his death, there would be gain on the house equal to the sale price in excess of your uncle's basis in the house. But, if this was his principal residence, he would be eligible for a capital gain exclusion from the sale of principal residence of up to $250,000. So, unless the gain is in excess of $250,000, there would be no non-excluded gain subject to capital gain tax.
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